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Extensions


Extension dictionaries were first introduced in ISO 32000-1:2008 for PDF 1.7, and were expanded in ISO 32000-2 for PDF 2.0. Their intent is to facilitate the documentation of extensions to the core PDF specification in PDF files so that other developers can detect and report them in their products.

The primary purpose of this PDF extensions list is to assist developers and stakeholders in providing consistent reporting of implementations and/or features contained within PDF files (regardless of whether the extensions are supported or not).

Below is a list of well-known and publicly documented PDF extensions. This list is not exhaustive. The PDF Association will consider including other PDF extensions via logging a new Issue in the related Github repository. The Github repository also contains a JSON representation of this data.

Prefix ISO_

PDF 2.0 Hash Algorithm extensions (SHA-3 and SHAKE256)

Specification: ISO/TS 32001:2022 Document management - Portable Document Format - Extensions to Hash Algorithm Support in ISO 32000-2 (PDF 2.0)

Developer Extension entries

BaseVersion name 2.0
ExtensionLevel integer 32001
ExtensionRevision text string :2022
URL string https://www.iso.org/standard/45874.html

Description

Extensions to the PDF 2.0 (ISO 32000-2) specification to support the use of the Secure Hash Algorithm - 3 (SHA-3) and SHAKE256 hash algorithms.

Hash algorithms and encryption are a fundamental part of PDF. ISO 32000-2 updated both hash algorithms and encryption, but in the time since that standard was published, new algorithms have been developed or risen to prominence.

To ensure that PDF remains relevant in the fast-moving world of cryptography and remains current with best practices, these techniques should be refreshed and updated regularly. This extension builds upon the mechanisms present in PDF and extends and enhances them to meet the latest needs of the industry.

Published by ISO TC 171 SC 2 WG 8.

PDF 2.0 Digital Signature extensions

Specification: ISO/TS 32002:2022 Document management - Portable Document Format - Extensions to Digital Signatures in ISO 32000-2 (PDF 2.0)

Developer Extension entries

BaseVersion name 2.0
ExtensionLevel integer 32002
ExtensionRevision text string :2022
URL string https://www.iso.org/standard/45875.html

Description

Extensions to the PDF 2.0 (ISO 32000-2) specification to support:

  • use of the NIST P-curve family of elliptical curves for digital signatures;
  • use of the Brainpool family of elliptical curves for digital signatures;
  • use of Edwards Curve (EdDSA) Ed448 and Ed25519 families of elliptical curves for digital signatures.

Digital signatures are a fundamental part of the ISO 32000 series. ISO 32000-2 contains updated digital signature support, but in the time since that standard was published, new algorithms have been developed or risen to prominence.

To ensure that PDF remains relevant in the fast-moving world of cryptography and remains current with best practices, these techniques should be refreshed and updated regularly. This extension builds upon the mechanisms present in PDF and extends and enhances them to meet the latest needs of the industry.

Published by ISO TC 171 SC 2 WG 8.

PDF 2.0 AES-GCM support

Specification: ISO/TS 32003:2023 Document management - Portable Document Format - Adding support of AES-GCM in PDF 2.0

Developer Extension entries

BaseVersion name 2.0
ExtensionLevel integer 32003
ExtensionRevision text string :2023
URL string https://www.iso.org/standard/45876.html

Description

Extension to the PDF 2.0 (ISO 32000-2) specification to support the Advanced Encryption Standard (AES)-Galois/Counter Mode (GCM) encryption algorithm.

The Galois/Counter Mode (GCM) is a block cipher mode of operation that was standardized for use with the Advanced Encryption Standard (AES) by the US National Institute for Standards and Technology (NIST). AES-GCM provides high-speed encryption and data integrity.

AES-GCM is an authenticated encryption algorithm: it provides confidentiality as well as ciphertext authentication. The two cryptographic primitives supplied by AES-GCM are referred to as authenticated encryption and authenticated decryption. The authenticated encryption function encrypts the confidential data and computes an authentication tag on both the ciphertext and, optionally, an additional authenticated data (AAD) payload. The authenticated decryption function decrypts the confidential data, contingent on the verification of the tag. Each of these functions is relatively efficient and able to be parallelized; consequently, high throughput implementations are possible in both hardware and software. The AES-GCM algorithm supports cipher key of size 128-bits, 192-bits and 256-bits. The block size is of 128 bits.

In PDF encryption, encryption is applied to individual streams and strings. Using AES-GCM therefore authenticates all individual ciphertexts, but a separate mechanism is required to achieve document- level integrity guarantees. One such mechanism is defined in ISO/TS 32004

Published by ISO TC 171 SC 2 WG 8.

PDF 2.0 Integrity protection in encrypted documents

Specification: ISO/TS 32004:2024 Document management - Portable Document Format - Integrity protection in encrypted documents in PDF 2.0

Developer Extension entries

BaseVersion name 2.0
ExtensionLevel integer 32004
ExtensionRevision text string :2024
URL string https://www.iso.org/standard/45877.html

Description

Extension to the PDF 2.0 (ISO 32000-2) specification for adding extensions to the Encrypt dictionary and trailer dictionary to provide integrity protection to the encrypted PDF document.

When encrypting documents, it is important to not only preserve the confidentiality of the encrypted material, but also to ensure that the receiving party can verify its integrity. Encryption mechanisms defined in ISO 32000-2:2020 currently only provide confidentiality without this authentication aspect.

This document describes a mechanism to protect the integrity of an encrypted PDF document using a Message Authentication Code (MAC), with key material derived from the file encryption key. Message authentication codes are distinct from digital signatures based on public-key cryptography. Digital signatures and message authentication codes have different but complementary security properties: a valid MAC created following this document proves knowledge of the file encryption key, whereas digital signatures as defined in ISO 32000-2:2020 do not have that property. The MAC mechanism described in this document is backwards compatible with ISO 32000-2:2020 and can also be used in PDF documents containing digital signatures.

Published by ISO TC 171 SC 2 WG 8.

PDF 2.0 RichMedia STEP AP 242 support

Specification: ISO/TS 24064:2023 Document management - Portable Document Format - RichMedia annotations conforming to the ISO 10303-242 (STEP AP 242) specification

Developer Extension entries

BaseVersion name 2.0
ExtensionLevel integer 24064
ExtensionRevision text string 1:2023
URL string https://www.iso.org/standard/77686.html

Description

Extension to the PDF 2.0 (ISO 32000-2) specification for adding the ISO 10303-242 (STEP AP 242) format as a valid format for 3D assets contained in a RichMedia annotation.

Published by ISO TC 171 SC 2 WG 7.

PDF 2.0 RichMedia glTF support

Specification: ISO/TS 32007:2024 Document management - Portable Document Format - RichMedia annotations conforming to glTF assets

Developer Extension entries

BaseVersion name 2.0
ExtensionLevel integer 32007
ExtensionRevision text string 1:2024
URL string https://www.iso.org/standard/45880.html

Description

Extension to the PDF 2.0 (ISO 32000-2) specification for adding adding the ISO/IEC 12113 (glTF) format as a valid format for 3D artworks contained in a RichMedia annotation.

Published by ISO TC 171 SC 2 WG 7.

Prefix ESIC

PAdES Document Security Store (DSS) and Document Time-stamp (DTS)

Specification: ETSI EN 319 142-1 - Electronic Signatures and Infrastructures (ESI); PAdES digital signatures; Part 1: Building blocks and PAdES baseline signatures

Developer Extension entries

BaseVersion name 1.7
ExtensionLevel integer 1
ExtensionRevision text string
URL string

Description

See https://www.etsi.org/deliver/etsi_en/319100_319199/31914201/01.02.01_60/en_31914201v010201p.pdf, clause 5.6.

PAdES baseline signature

Specification: ETSI EN 319 142-1 - Electronic Signatures and Infrastructures (ESI); PAdES digital signatures; Part 1: Building blocks and PAdES baseline signatures

Developer Extension entries

BaseVersion name 1.7
ExtensionLevel integer 2
ExtensionRevision text string
URL string

Description

See https://www.etsi.org/deliver/etsi_en/319100_319199/31914201/01.02.01_60/en_31914201v010201p.pdf, clause 5.6.

Prefix ESIX

Additional PAdES signatures profiles

Specification: ETSI EN 319 142-2 - Electronic Signatures and Trust Infrastructures (ESI); PAdES digital signatures; Part 2: Additional PAdES signatures profiles

Developer Extension entries

BaseVersion name 1.7
ExtensionLevel integer 1
ExtensionRevision text string
URL string

Description

See https://www.etsi.org/deliver/etsi_en/319100_319199/31914202/01.02.01_60/en_31914202v010201p.pdf, clause 6.3.4.

PAdES for XML Content - Profiles for XAdES signatures

Specification: ETSI TS 102 778-5 - Electronic Signatures and Infrastructures (ESI); PDF Advanced Electronic Signature Profiles; Part 5: PAdES for XML Content - Profiles for XAdES signatures

Developer Extension entries

BaseVersion name 1.7
ExtensionLevel integer 1
ExtensionRevision text string
URL string

Description

See https://www.etsi.org/deliver/etsi_ts/102700_102799/10277805/01.01.02_60/ts_10277805v010102p.pdf, clause 5.4.

Prefix ADBE

Acrobat Implementation of the PDF Specification

Specification: Acrobat Implementation of the PDF Specification (BaseVersion: 1.7 ExtensionLevel: 1). April 2007. Adobe® Acrobat® 8.1

Developer Extension entries

BaseVersion name 1.7
ExtensionLevel integer 1
ExtensionRevision text string
URL string

Description

Adobe Extension Level 1 added the following features:

  • Support for ECMA-363 U3D 3rd edition;
  • PRC in 3D annotations;
  • rich text conventions based on XFA 2.5 and 2.6;

Available via the PDF Association's PDF Specification Archive.

Adobe Extension Level 3 for PDF 1.7

Specification: Adobe® Supplement to the ISO 32000 BaseVersion: 1.7 ExtensionLevel: 3. June 2008. Adobe® Acrobat® SDK Version 9.0

Developer Extension entries

BaseVersion name 1.7
ExtensionLevel integer 3
ExtensionRevision text string
URL string

Description

Adobe Extension Level 3 for ISO 32000-1 added many features that are now officially part of in PDF 2.0 (ISO 32000-2). This includes:

  • Extension identification;
  • Bates numbering page artifact;
  • Enforced viewer preferences;
  • 3D measurement and markup;
  • Annotation tab ordering for accessibility;
  • Portable collections;
  • RichMedia annotations;

Available via the PDF Association's PDF Specification Archive.

Adobe Extension Level 5 for PDF 1.7

Specification: Adobe® Supplement to the ISO 32000 BaseVersion: 1.7 ExtensionLevel: 5. June 2009. Adobe® Acrobat® SDK Version 9.1

Developer Extension entries

BaseVersion name 1.7
ExtensionLevel integer 5
ExtensionRevision text string
URL string

Description

Available via the PDF Association's PDF Specification Archive.

PAdES Document Security Store (DSS) and Document Time-stamp (DTS)

Specification:

Developer Extension entries

BaseVersion name 1.7
ExtensionLevel integer 8
ExtensionRevision text string
URL string

Description

See mention in https://www.etsi.org/deliver/etsi_en/319100_319199/31914201/01.02.01_60/en_31914201v010201p.pdf, NOTE in clause 5.6

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