ISO 19005-4:2020

Document management - Electronic document file format for long-term preservation - Part 4: Use of ISO 32000-2 (PDF/A-4)

This document specifies the use of the Portable Document Format (PDF) 2.0, as formalized in ISO 32000-2:-, for preserving the static visual representation of page based electronic documents over time in addition to allowing any type of other content to be included as an embedded file or attachment. This document does not apply to: - specific processes for converting paper or electronic documents to the PDF/A format; - specific technical design, user interface, implementation, or operational details of rendering; - specific physical methods of storing these documents such as media and storage conditions; - required computer hardware and/or operating systems.

Gestion de documents — Format de fichier des documents électroniques pour une conservation à long terme — Partie 4: Titre manque

General Information

• Status: Published
• Publication Date: 16-Nov-2020
• ICS: 35.240.30 - IT applications in information, documentation and publishing
• ICS: 37.100.99 - Other standards related to graphic technology
• Technical Committee: ISO/TC 171/SC 2 - Document file formats, EDMS systems and authenticity of information
• Drafting Committee: ISO/TC 171/SC 2/WG 5 - Joint TC 171/SC 2 - TC 42 - TC 46/SC 11 - TC 130 WG: Document management applications - Application issues - PDF/A
• Parallel Committee: ISO/TC 42 - Photography
• Current Stage: 9092 - International Standard to be revised
• Start Date: 12-May-2023
• Completion Date: 13-Dec-2025

Overview

ISO 19005-4:2020 - PDF/A-4 specifies how to use the Portable Document Format (PDF) 2.0 (ISO 32000-2) for the long‑term preservation of page‑based electronic documents. The standard focuses on preserving the static visual representation of documents over time while allowing other content (for example, original source files or attachments) to be included as embedded files. It is part of the ISO 19005 series (PDF/A) and builds on PDF 2.0 features to support archival, accessibility and richer semantics without prescribing conversion workflows, rendering implementations, storage media, or required hardware/OS.

Key technical topics and requirements

ISO 19005-4 defines the set of permitted PDF 2.0 features and constraints needed for reliable preservation. Major technical topics include:

• Conformance: rules for conforming files and conforming processors (viewers/validators) to ensure long‑term fidelity.
• File structure: headers, trailers, cross‑reference tables, indirect objects, linearized PDF considerations.
• Graphics and color: permitted graphics operators, color spaces, output intents and rules for consistent visual rendering.
• Fonts: embedding and usage requirements to preserve text appearance.
• Images and XObjects: supported image types and handling of external/inline objects.
• Annotations and interactive forms: restrictions and handling of annotations, forms (including XFA considerations) to preserve intended presentation.
• Digital signatures: signature profiles, validation and proof‑of‑existence considerations for signed archival documents.
• Metadata and provenance: required and recommended metadata streams, file identifiers, version identification and provenance information to support discovery and authenticity.
• Logical structure and accessibility: tagged PDF features and semantics to preserve document structure and machine‑readable text order.
• Embedded files and optional content: rules for including other files inside a PDF/A (not guaranteeing their suitability for long term storage, but permitting embedding).
• Specialized profiles: normative annexes defining PDF/A‑4f (embedded files) and PDF/A‑4e (engineering) for domain‑specific use cases.
• Exclusions: the standard does not cover conversion processes, rendering interface design, physical storage methods, or hardware/OS requirements.

Practical applications and users

ISO 19005-4 (PDF/A-4) is intended for organizations that need dependable, standards‑based archival of digital documents:

• Archives, libraries and cultural heritage institutions
• Government and regulatory bodies (records retention, FOIA)
• Enterprises for legal/compliance recordkeeping
• Engineering and CAD workflows (PDF/A‑4e)
• Software vendors producing PDF creation, validation and rendering tools
• Digital preservation specialists and IT/infrastructure teams

Benefits include predictable visual rendering over time, embedded provenance and metadata for authenticity, and the option to package original files alongside archival PDF representations.

Related standards

• ISO 32000-2 - PDF 2.0 (base format used by PDF/A-4)
• Other parts of the ISO 19005 (PDF/A) series (PDF/A-1, -2, -3, etc.) for alternative archival profiles and use cases

Keywords: ISO 19005-4, PDF/A-4, PDF 2.0, ISO 32000-2, long-term preservation, archival PDF, embedded files, digital signatures, metadata, conformance.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 19005-4
First edition
2020-11
Document management — Electronic
document file format for long-term
preservation —
Part 4:
Use of ISO 32000-2 (PDF/A-4)
Reference number
©
ISO 2020
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Notation . 2
5 Conformance . 3
5.1 Conforming Files . 3
5.2 Conforming Processor . 4
6 Technical requirements . 4
6.1 File structure . 4
6.1.1 General. 4
6.1.2 File header . 4
6.1.3 File trailer . . . 4
6.1.4 Cross reference table . 4
6.1.5 String objects . 5
6.1.6 Stream objects . 5
6.1.7 Name objects . 5
6.1.8 Indirect objects . 5
6.1.9 Inline image dictionaries . 5
6.1.10 Linearized PDF . 6
6.1.11 Permissions . 6
6.1.12 Document catalog dictionary . 6
6.2 Graphics . 6
6.2.1 General. 6
6.2.2 Content streams. 6
6.2.3 Output intent . 7
6.2.4 Colour spaces . 7
6.2.5 Extended graphics state. 9
6.2.6 Flatness .10
6.2.7 Images .10
6.2.8 XObjects .11
6.2.9 Transparency .11
6.2.10 Fonts .11
6.3 Annotations.15
6.3.1 Annotation types .15
6.3.2 Annotation dictionaries .15
6.3.3 Annotation appearances .15
6.3.4 Display of annotation contents .16
6.4 Interactive forms .16
6.4.1 General.16
6.4.2 XFA forms .16
6.5 Digital signatures .16
6.5.1 General.16
6.5.2 Signature profiles .17
6.5.3 Proof of existence .17
6.5.4 Validation .17
6.6 Action .18
6.6.1 General.18
6.6.2 Handling of JavaScript actions .18
6.6.3 Trigger events .18
6.6.4 Handling of GoToR, GoToE, URI and SubmitForm actions .19
6.7 Metadata .19
6.7.1 General.19
6.7.2 Metadata streams .19
6.7.3 Version identification . .20
6.7.4 File identifiers .20
6.7.5 File provenance information .21
6.8 Logical structure .21
6.9 Embedded files .21
6.10 Optional content .22
6.11 Use of alternate presentations and transitions .23
6.12 Document requirements .23
6.13 Print scaling .23
6.14 Geospatial .23
6.15 Measurement Properties .23
Annex A (normative) Requirements for a PDF/A with Embedded Files (PDF/A-4f) .24
Annex B (normative) Requirements for a PDF/A for Engineering (PDF/A-4e) .25
Bibliography .27
iv © ISO 2020 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 171, Document management applications,
SC 2, Document file formats, EDMS systems and authenticity of information.
A list of all parts in the ISO 19005 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
Introduction
PDF is a digital format for representing page-based documents. PDF files can be created natively in PDF
form, converted from other electronic formats or digitized from paper, microform, or other hard copy
format. Businesses, governments, libraries, archives and other institutions and individuals around the
world use PDF to represent considerable bodies of important information. Much of this information
needs to be kept for substantial lengths of time; some needs to be kept permanently. These PDF files
need to remain useable and accessible across multiple generations of technology. However, the inclusive,
feature-rich nature of the format requires that constraints be placed on its use to make it suitable for
the long-term preservation of electronic documents. The future use of, and access to, these objects
depends upon maintaining their visual appearance as well as their higher-order properties, such as
the logical organization of pages, sections, and paragraphs, machine recoverable text stream in natural
reading order, and a variety of administrative, preservation and descriptive metadata.
This document is part of a series of documents, of which this is part 4. This allows future parts to be
created without rendering this document or applications based on this document obsolete.
The primary purpose of ISO 19005 is to define a file format based on PDF, known as PDF/A, which
provides a mechanism for representing electronic documents in a manner that preserves their visual
appearance over time, independent of the tools and systems used for creating, storing or rendering the
files. Some parts of ISO 19005 also define a framework for representing the logical structure and other
semantic information of electronic documents within conforming files. These goals are accomplished
by identifying the set of PDF components that can be used, and restrictions on the form of their use,
within conforming PDF/A files.
Parts 3 & 4 in this series enable PDF documents to serve as containers for other file formats, so that
a single physical file can contain not only the visual representation but also other representations
including the original authored version, richer semantic formats, and others. This standard does not
address the long-term suitability of formats, that may be embedded, other than those compliant with
any part of this document.
1)
This document is based on PDF version 2.0 (as defined in ISO 32000-2:— ) and as such provides
recommendations in how to properly archive content that uses some of the newer features present
there including page level output intents, associated files and improvements to tagged PDF.
This document also introduces some new directions in archiving non-static content that can be present
in PDF documents, such as form fields and ECMAScript. It seeks to preserve more information in the
file (by not requiring its removal during the archival process) and puts a greater burden on conforming
viewers to ensure that such information does not alter the visual appearance of the file during
consumption.
By itself, PDF/A does not necessarily ensure that the visual appearance of the content accurately
reflects any original source material used to create the conforming file; e.g. the process used to create
a conforming file might substitute fonts, reflow text, downsample images or use lossy compression.
Organizations that need to ensure that a conforming file is an accurate representation of original source
material might need to impose additional requirements on the processes that generate the conforming
file beyond those imposed by this document. In addition, it is important for those organizations to
implement policies and practices regarding the inspection of conforming files for correct visual
appearance.
This document is one component of an organization's electronic archival environment for long-term
retention of documents. Successful implementation of this document for archival purposes depends upon:
— the retention requirements of an organization's archival environment, records management policies
[2]
and procedures as specified in ISO 15489-1 ;
1) Under preparation. Stage at the time of publication: ISO/FDIS 32000-2.
vi © ISO 2020 – All rights reserved

— any additional conditions necessary to ensure the persistence of electronic documents and
[1]
their characteristics over time, including, but not limited to, those defined by ISO 14721 , and
[3]
ISO/TR 18492 ;
— quality assurance processes necessary to verify conformance with applicable requirements and
conditions; e.g. an inspection regime to verify the quality and integrity of converted source data.
This document is intended to lead to the development of various applications that read, render,
write and validate conforming files. Different applications will incorporate various capabilities to
prepare, interpret and process conforming files based on needs as perceived by the suppliers of those
applications. However, it is important to note that a conforming application needs to be able to read and
process appropriately all files complying with a specified conformance level.
This document (in conjunction with its normative references) provides sufficient information to
interpret any conforming PDF/A-4 file.
The PDF Association may maintain an ongoing series of application notes for guiding developers and
users of this document. These application notes are available at https:// www .pdfa .org/ . The PDF
Association will also retain copies of the specific non-ISO normative references of this document which
are publicly available electronic documents.
INTERNATIONAL STANDARD ISO 19005-4:2020(E)
Document management — Electronic document file format
for long-term preservation —
Part 4:
Use of ISO 32000-2 (PDF/A-4)
1 Scope
This document specifies the use of the Portable Document Format (PDF) 2.0, as formalized in
ISO 32000-2:—, for preserving the static visual representation of page based electronic documents over
time in addition to allowing any type of other content to be included as an embedded file or attachment.
This document does not apply to:
— specific processes for converting paper or electronic documents to the PDF/A format;
— specific technical design, user interface, implementation, or operational details of rendering;
— specific physical methods of storing these documents such as media and storage conditions;
— required computer hardware and/or operating systems.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 14533-3, Processes, data elements and documents in commerce, industry and administration — Long term
signature profiles — Part 3: Long term signature profiles for PDF Advanced Electronic Signatures (PAdES)
ISO 16684-2, Graphic technology — Extensible metadata platform (XMP) — Part 2: Description of XMP
schemas using RELAX NG
ISO 19005-1, Document management — Electronic document file format for long-term preservation —
Part 1: Use of PDF 1.4 (PDF/A-1)
ISO 19005-2, Document management — Electronic document file format for long-term preservation —
Part 2: Use of ISO 32000-1 (PDF/A-2)
ISO 32000-2:—, Document management — Portable document format — Part 2: PDF 2.0
XMP Specification Part 2: Additional Properties – Adobe Systems – https:// www .adobe .com/ content/
dam/ acom/ en/ devnet/ xmp/ pdfs/ XMPSDKReleasecc -2020/ XMPSpecificationPart2 .pdf
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
end-of-file marker
five-character sequence %%EOF marking the end of a PDF file
3.2
extension schema
conforming XMP schema that is not defined in the XMP Specification nor part 1 or part 2 of this
document
3.3
font
identified collection of graphics that may be glyphs or other graphic elements
[SOURCE: ISO 32000-2:—]
3.4
font program
software program written in a special-purpose language, such as the Type 1, TrueType, or OpenType font
format, that is understood by a specialized font (3.3) interpreter
[SOURCE: ISO 32000-2:—]
3.5
interactive processor
processor (3.8) that requires or allows human interaction with the content and other objects contained
in the document during the software's processing phase
Note 1 to entry: A file viewing tool is an example of an interactive processor; a raster image processor is an
example of a processor that is not interactive.
3.6
long-term
period of time long enough for there to be concern about the impacts of changing technologies
3.7
PDF
Portable Document Format
file format defined in ISO 32000-2:—
3.8
processor
software application that is able to read and process conforming files
3.9
writer
software application that is able to write conforming files
3.10
XMP packet
structured wrapper for serialized XMP metadata
[SOURCE: ISO 32000-2:—]
4 Notation
PDF operators, PDF keywords, the names of keys in PDF dictionaries, and other predefined names are
written in bold sans serif font; operands of PDF operators or values of dictionary keys are written in
italic font. Some names can also be used as values, depending on the context, and so the styling of the
content will be context specific.
EXAMPLE 1 The Default value for the TR2 key.
2 © ISO 2020 – All rights reserved

Token characters used to delimit objects and describe the structure of PDF files, as defined in
ISO 32000-2: —, 7.2.1, may be identified by their ISO/IEC 646 character name written in upper case in
bold font followed by a parenthetic two digit hexadecimal character value with the suffix “h”.
EXAMPLE 2 CARRIAGE RETURN (0Dh).
Text string characters, as defined by ISO 32000-2:—, 7.9.2, may be identified by their ISO/IEC 10646
character name written in uppercase in bold font followed by a parenthetic four digit hexadecimal
character code value with the prefix “U+”.
EXAMPLE 3 EN SPACE (U+2002).
The following terms, referring to this specification or parts thereof, are recommended when the full
ISO name is not being used:
— “PDF/A” – a synonym for the ISO 19005 family of standards;
— “PDF/A-1” – a synonym for ISO 19005-1;
— “PDF/A-1a” – a synonym for ISO 19005-1 Level A conformance;
— “PDF/A-1b” – a synonym for ISO 19005-1 Level B conformance;
— “PDF/A-2” – a synonym for ISO 19005-2;
— “PDF/A-2a” – a synonym for ISO 19005-2 Level A conformance;
— “PDF/A-2b” – a synonym for ISO 19005-2 Level B conformance;
— “PDF/A-2u” – a synonym for ISO 19005-2 Level U conformance;
— “PDF/A-3a” – a synonym for ISO 19005-3 Level A conformance;
— “PDF/A-3b” – a synonym for ISO 19005-3 Level B conformance;
— “PDF/A-3u” – a synonym for ISO 19005-3 Level U conformance;
— “PDF/A-4” – a synonym for ISO 19005-4;
— “PDF/A-4e” – a synonym for ISO 19005-4 Level E conformance;
— “PDF/A-4f” – a synonym for ISO 19005-4 Level F conformance;
5 Conformance
5.1 Conforming Files
This document defines a file format for representing electronic documents known as “PDF/A-4”.
Conforming PDF/A-4 files shall adhere to all requirements of ISO 32000-2:— as modified by this document.
A conforming file may include any valid ISO 32000-2:— feature that is not explicitly forbidden by this
document. Features described in specifications which are not explicitly described in ISO 32000-2:—,
should not be used. Features described as deprecated in ISO 32000-2:— shall not be used.
NOTE A conforming file is not obligated to use any PDF feature other than those explicitly required by
ISO 32000-2:— or this document.
The proper mechanism by which a file can presumptively identify itself as being a conforming PDF/A-4
file is described in 6.7.3.
5.2 Conforming Processor
A conforming processor shall comply with all requirements regarding processor functional behaviour
specified in this document. The requirements of this document with respect to processor behaviour
are stated in terms of general functional requirements applicable to all conforming processors. This
document does not prescribe any specific technical design, user interface or implementation details of
conforming processors.
The rendering and other processing of conforming files shall be performed as defined in ISO 32000-2:—
subject to the additional restrictions specified by this document. Features described in specifications
that are not explicitly described in ISO 32000-2:— should be ignored by conforming processors.
Conforming PDF/A-4 processors shall read and process appropriately all conforming PDF/A-4 files.
6 Technical requirements
6.1 File structure
6.1.1 General
6.1.2 to 6.1.13 address overall file format issues and the base elements that form the general structure
of a conforming file.
Any data contained in a conforming file that is not described in ISO 32000-2:— or this document should
be ignored by a conforming processor and shall not be used to render content on a page.
6.1.2 File header
The file header shall begin at byte zero and shall consist of “%PDF-2.n” followed by a single EOL marker,
where ‘n’ is a single digit number between 0 (30h) and 9 (39h).
NOTE 1 This clarifies the requirement in ISO 32000-2:—, 7.5.2
The aforementioned EOL marker shall be immediately followed by a % (25h) character followed by at
least four bytes, each of whose encoded byte values shall have a decimal value greater than 127.
NOTE 2 The presence of encoded byte values greater than decimal 127 near the beginning of a file is used by
various software tools and protocols to classify the file as containing 8-bit binary data that needs to be preserved
during processing.
6.1.3 File trailer
No data shall follow the last end-of-file marker as described in ISO 32000-2:—, 7.5.5.
The Encrypt key shall not be present in the trailer dictionary.
NOTE 1 The explicit prohibition of the Encrypt key has the implicit effect of disallowing encryption and
password-protected access permissions.
The Info key shall not be present in the trailer dictionary of PDF/A-4 conforming files unless there
exists a PieceInfo entry in the document catalog dictionary. If a document information dictionary is
present, it shall only contain a ModDate entry.
NOTE 2 This makes normative the deprecation of this feature in ISO 32000-2:—, 14.3.3, except when needed
for a PieceInfo dictionary.
6.1.4 Cross reference table
The xref keyword and the cross-reference subsection header shall be separated by a single EOL marker.
4 © ISO 2020 – All rights reserved

Any indirect object whose offset is not referenced in any cross-reference table nor in any cross reference
stream shall be exempt from all requirements of this document and may be ignored by a conforming
processor. If a conforming processor chooses not to ignore such indirect objects, they shall never
influence the way content is rendered.
6.1.5 String objects
The number of hexadecimal digits in a hexadecimal string shall always be even.
NOTE This avoids the provision in ISO 32000-2: — about the absence of the final hexadecimal digit.
6.1.6 Stream objects
6.1.6.1 General
The value of the Length key specified in the stream dictionary shall match the number of bytes in the
file following the LINE FEED (0Ah) character after the stream keyword and preceding the EOL marker
before the endstream keyword.
A stream dictionary shall not contain the F, FFilter, or FDecodeParams keys.
NOTE 1 These keys are used to point to data external to the file. The explicit prohibition of these keys has the
implicit effect of disallowing external content that can create external dependencies and complicate preservation
efforts.
NOTE 2 Since an inline image dictionary is not a stream object, this provision allows the presence of the F key
in an inline image dictionary as the abbreviation for Filter.
6.1.6.2 Filters
All standard stream filters listed in ISO 32000-2:—, 7.4, Table 6 may be used, with the exception of
LZWDecode. Filters that are not listed in ISO 32000-2:—, 7.4, Table 6 shall not be used.
In addition, the Crypt filter shall not be used unless the value of the Name key in the decode parameters
dictionary is Identity.
NOTE The Crypt filter is used to apply encryption and access control to the file.
6.1.7 Name objects
Font names, names of colourants in Separation and DeviceN colour spaces, and structure type names -
after expansion of character sequences escaped with a NUMBER SIGN (23h), if any - shall be valid UTF-8
character sequences.
NOTE These requirements make normative the recommendations set out in ISO 32000-2:—, 7.3.5.
All other name objects should adhere to these same restrictions.
6.1.8 Indirect objects
The object number and generation number shall be separated by a single white-space character. The
generation number and obj keyword shall be separated by a single white-space character.
The object number and endobj keyword shall each be preceded by an EOL marker. The obj and endobj
keywords shall each be followed by an EOL marker.
6.1.9 Inline image dictionaries
The value of the F key in the Inline Image dictionary shall not be LZW, LZWDecode, Crypt or a value not
listed in ISO 32000-2:—, 8.9.7, Table 92 or an array containing any such value.
6.1.10 Linearized PDF
Linearization shall be permitted but any linearization information present within a file should be
ignored by conforming processor.
NOTE As defined in ISO 32000-2:—, Annex F, a PDF is not linearized if the value of the L key in the
linearization dictionary does not match the actual length of the PDF file. This implies that an incremental update
to a linearized PDF will render it non-linearized.
6.1.11 Permissions
No keys other than UR3 and DocMDP shall be present in a permissions dictionary (ISO 32000-2:—,
12.8.6, Table 263).
NOTE These restrictions are present to ensure that functionality such as obsolete versions of the “User
Rights” dictionary do not appear in a document conforming to this document.
6.1.12 Document catalog dictionary
If the Version key is present in the document catalog dictionary, the first character in its value shall
be a 2 (32h) and the second character of its value shall be a PERIOD (2Eh) (decimal point). The third
character shall be a decimal digit. The number of characters of the value of the Version key shall be
exactly 3.
NOTE This clarifies the requirement in ISO 32000-2:—, 7.5.2
6.2 Graphics
6.2.1 General
Clauses 6.2.2 to 6.2.10 describe restrictions that shall be placed on both conforming files and processors
with respect to the graphical elements described in ISO 32000-2:—, 7.8. A conforming processor
shall render these graphical elements onto their respective PDF pages according to the rendering
requirements of ISO 32000-2:— as modified by this document.
A conforming interactive processor may choose to put additional user interface elements around, above
or below the graphical elements of the page. These user interface elements may be a presentation of
other PDF objects (such as bookmarks or page thumbnails) or they may represent non-PDF objects.
In all cases, the user interface elements and their contents shall not be required to conform to the
requirements of 6.2.2 to 6.2.10.
6.2.2 Content streams
Content streams shall not contain any operators not defined in ISO 32000-2:—, even if such operators
are bracketed by the BX/EX compatibility operators.
NOTE Content streams, as defined in ISO 32000-2:—, 7.8.2, are used for page descriptions, Form XObjects,
Type 1 Patterns, Type 3 glyph descriptions, as well as for the appearances of annotations.
A content stream that references other objects, such as images and fonts that are necessary to fully
render or process the stream, shall have an explicitly associated resources dictionary as described
in ISO 32000-2:—, 7.8.3. Such resource dictionaries shall define all named resources referenced by
this content stream. Any named resource present in the resource dictionary, but whose name is not
referenced from the associated content stream, is not used for rendering and therefore shall be exempt
from all requirements of this document except those in 6.1.6 - 6.1.9.
6 © ISO 2020 – All rights reserved

6.2.3 Output intent
A conforming file may specify the colour characteristics of the device on which it is intended to
be rendered by using a PDF/A OutputIntent. A PDF/A OutputIntent is defined as an output intent
dictionary (ISO 32000-2:—, 14.11.5) which shall contain an S key whose value shall be GTS_PDFA1 and
a DestOutputProfile key whose value shall be a valid ICC profile stream. A PDF/A OutputIntent may be
present either in the OutputIntents array of the document catalog dictionary or in the OutputIntents
array of a page dictionary. It is also possible that a document may have a PDF/A OutputIntent in the
document catalog dictionary and then an alternative one for certain pages.
NOTE 1 PDF/A requires that an output intent dictionary be present when uncalibrated colour spaces are used
(see 6.2.4.3 for more details). It has this requirement in order to ensure reliable rendering of colour through the
indirect use of the PDF/A OutputIntent profile provided.
NOTE 2 The value of GTS_PDFA1 was maintained for this part of ISO 19005 to enable greater compatibility
with all parts of ISO 19005.
In addition, the DestOutputProfileRef key, as defined in ISO 32000-2:—, 14.11.5, Table 401, shall not
be present in any output intent dictionary.
NOTE 3 Disallowing the DestOutputProfileRef key maintains the intent of this document of ensuring self-
contained documents with no external references. However, it does mean that a single PDF is unable to be
compliant with both PDF/A-4 and PDF/X-4p or with both PDF/A-4 and PDF/X-6p.
If the document does not contain a document-level PDF/A OutputIntent (present in the OutputIntents
array of the document catalog dictionary), then for any page whose contents are not fully specified using
device-independent colour (as defined in 6.2.4.1), the page dictionary shall contain an OutputIntents
key whose value shall be an array containing a PDF/A OutputIntent, representing the page-level PDF/A
OutputIntent. When a page-level PDF/A OutputIntent is present, then it shall be considered the current
PDF/A OutputIntent when processing that page, otherwise (if present) the document-level PDF/A
OutputIntent shall be considered current.
If any OutputIntents array contains more than one entry, such as may be the case where a file is
compliant with this document and at the same time with PDF/X or PDF/E, then all entries that contain
a DestOutputProfile key shall have as the value of that key the same indirect object, which shall be a
valid ICC profile stream.
The profile stream that is the value of the DestOutputProfile key shall either be an output device
profile (Device Class = “prtr”) or a monitor profile (Device Class = “mntr”). The profiles shall have a
colour space of either “GRAY”, “RGB ”, or “CMYK”. If present in the DestOutputProfile stream object,
the Alternate key shall be ignored by a PDF/A-4 conforming processor.
6.2.4 Colour spaces
6.2.4.1 General
All colours shall be specified in a device-independent manner, either directly by the use of device-
independent colour spaces, or indirectly by the means of the DestOutputProfile in the PDF/A
OutputIntent. A conforming file may use any colour space specified in ISO 32000-2:—, except as
restricted in 6.2.4.2 to 6.2.4.5.
NOTE Specifying colour in a device-independent manner as described within 6.2.4 enables predictable
colour rendering based on a colorimetric definition and without reliance on heuristic assumptions or on
information external to the conforming file. It also provides a mechanism whereby a colorimetric definition can
be associated with device-dependent colour data.
6.2.4.2 ICCBased colour spaces
The profile that forms the stream of an ICCBased colour space shall conform to ISO 32000-2:—, 8.6.5.5.
A conforming processor shall render ICCBased colour spaces as specified by ISO 32000-2:—, and shall
not use the Alternate colour space specified in an ICC profile stream dictionary.
Overprint mode (as set by the OPM value in an ExtGState dictionary) shall not be one (1) when an
ICCBased CMYK colour space is used and when overprinting for stroke or fill or both is set to true.
NOTE 1 This prohibition avoids unpredictable overprinting behaviour when overprint mode is 1 if implicit
colour conversion is applied as described in ISO 32000-2:—, 8.6.7.
An ICCBased colour space shall not be used where the profile is a CMYK destination profile and is
identical to that in the current PDF/A OutputIntent or the current transparency blending colorspace.
Profiles shall be treated as identical if:
— the ICCBased colour space and the output intent use indirect references to the same embedded
profile stream; or
— MD5 hash values for the two profiles are the same. MD5 values are read from the value of the Profile
ID field within each profile, if present and if not set as zero. If no MD5 value is included in each profile,
then a value shall be calculated following the methodology set out in of ISO 15076-1:2010, 7.2.18.
NOTE 2 This avoids the possibility of output differing depending on whether a renderer applies the implicit
colour conversion described on ISO 32000-2:—, 8.6.5.7.
6.2.4.3 Uncalibrated/Device colour spaces
DeviceRGB shall only be used if a device independent DefaultRGB colour space has been set when the
DeviceRGB colour space is used or if the current transparency blending space, when the DeviceRGB
colour space is used, is a device independent RGB-based colour space or the current PDF/A OutputIntent,
when the DeviceRGB colour space is used, contains an ‘RGB ’ destination profile.
DeviceCMYK shall only be used if a device independent DefaultCMYK colour space has been set
when the DeviceCMYK colour space is used or if the current transparency blending space, when the
DeviceCMYK colour space is used, is a device independent CMYK-based colour space or the current
PDF/A OutputIntent, when the DeviceCMYK colour space is used, contains a ‘CMYK’ destination profile.
DeviceGray shall only be used if a device independent DefaultGray colour space has been set when the
DeviceGray colour space is used, or if a PDF/A OutputIntent is in effect.
NOTE As described in ISO 32000-2:—, 8.6.5.6, colours that are specified in a device colour space
(DeviceGray, DeviceRGB, or DeviceCMYK) are device dependent. By setting default colour spaces, a conforming
writer can request that such colours be systematically transformed (remapped) into device-independent CIE-
based colour spaces.
When rendering colours specified in DeviceRGB or DeviceCMYK, and no matchi
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