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Format

Acrobat PDF/A - Portable Document Format

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Summary

Name
Acrobat PDF/A - Portable Document Format
Version
1b
Identifiers
  • MIME: application/pdf
  • Apple Uniform Type Identifier: com.adobe.pdf
  • PUID: fmt/354
Format type
Page Description
Disclosure
Full
Description
The Portable Document Format/ Archive is a format designed for long term preservation by Adobe Systems. PDF/A is a simplified version of PDF 1.4, with all of the features from PDF 1.4 that would impede long term preservation removed. Removed features include Javascript, Audio/Visual content, LZW compression and encryption. A major principle of PDF/A is that it is self contained and not reliant on externalities thus all font and colour information is encoded into the file. PDF/A files are larger than other types of PDF files due to the need for embedded information. PDF/A supports two levels of compliance PDF/A1-a (Accessible) and PDF/A1-b (Basic). PDF/A1-a is fully ISO 19005-1:2005 (PDF/A-1) compliant whereas PDF/A1-b is less stringent and not compliant. PDF/A1-a requires tagged PDF and Unicode whereas PDF/A1-b does not. The signature identification proposed for PDF/A 1b has been tested against a number of PDF/A and PDF files for verification. However, PDF itself is a complex format, and while the PDF/A 1b signature contained in PRONOM will identify many PDF/A 1b files, DROID can only identify what a file asserts itself to be. As there are a number of ways in which PDF/A 1b files can violate the PDF/A 1b conformance, which can not be spotted until the file is parsed, it is recommended that PDF files are tested against validation software when attempting to confirm identification. Further information concerning PDF/A violations, and a test suite of PDF items which fail to conform to PDF/A standards, can be found at http://www.pdfa.org/2011/08/isartor-test-suite/
File extensions
pdf
Source
Digital Preservation Department / The National Archives

Relationships

Has lower priority than
Has priority over

Internal signatures

Acrobat PDF/A 1b 1

Note
Describes a signature for the PDF/A format with 1b conformance. Identifies the PDF header (1.3 through to 1.7) and byte sequence which equals - xmlns:pdfaid="http://www.aiim.org/pdfa/ns/id/">.<pdfaid:part>1</pdfaid:part>.<pdfaid:conformance>B</pdfaid:conformance>. Which is the PDF/A identification namespace within the PDF/A meta-data, and the 1b conformance. See ISO 19005-1:2005 and Technical Corrigendum 1 for further information.

Byte sequences

Min Frag Length
Absolute from BOF
Offset
0
Max offset
144
Byte Sequence
255044462D312E[30:37]
Endianness
None
Min Frag Length
Variable
Offset
None
Max offset
None
Byte Sequence
786D6C6E733A7064666169643D(22|27)687474703A2F2F7777772E6169696D2E6F72672F706466612F6E732F6964*7064666169643A70617274(3D22|3D27|3E)31(22|27|3C2F7064666169643A706172743E){0-120}7064666169643A636F6E666F726D616E6365(3E|3D22|3D27)42(22|27|3C2F7064666169643A636F6E666F726D616E63653E)
Endianness
None

Acrobat PDF/A 1b 2

Note
Describes a signature for the PDF/A format with 1b conformance. Identifies the PDF header (1.3 through to 1.7) and byte sequence which equals - xmlns:pdfaid="http://www.aiim.org/pdfa/ns/id/">.<pdfaid:conformance>B</pdfaid:conformance>.<pdfaid:part>1</pdfaid:part>. Which is the PDF/A identification namespace within the PDF/A meta-data, and the 1b conformance. See ISO 19005-1:2005 and Technical Corrigendum 1 for further information.

Byte sequences

Min Frag Length
Absolute from BOF
Offset
0
Max offset
144
Byte Sequence
255044462D312E[30:37]
Endianness
None
Min Frag Length
Variable
Offset
None
Max offset
None
Byte Sequence
786D6C6E733A7064666169643D(22|27)687474703A2F2F7777772E6169696D2E6F72672F706466612F6E732F6964*7064666169643A636F6E666F726D616E6365(3E|3D22|3D27)42(22|27|3C2F7064666169643A636F6E666F726D616E63653E){0-120}7064666169643A70617274(3D22|3D27|3E)31(22|27|3C2F7064666169643A706172743E)
Endianness
None

Changelog

  • Added in V101

    Release date
    15 February 2022

    Acrobat PDF/A - Portable Document Format (1b): Extension to byte gap between part and conformance tags added to both signatures. Submitted by The National Archives of the Czech Republic.

    Acrobat PDF/A - Portable Document Format (1b): Signature researched and samples provided by The National Archives of the Czech Republic.

  • Updated in V89

    Release date
    8 March 2017

    Acrobat PDF/A - Portable Document Format 1b: Adjusted signatures due to findings by Koninklijke Bibliotheek

  • Updated in V88

    Release date
    27 September 2016

    Acrobat PDF/A - Portable Document Format 1b: Gave priority over x-fmt/453 - TrueType Font. Suggested by Archives New Zealand.

  • Updated in V81

    Release date
    18 February 2015

    Acrobat PDF/A 1b: MIME Type added. Submitted by Docuteam.

  • Updated in V74

    Release date
    31 March 2014

    Acrobat (PDF/A) Portable Document Format 1b: Increased flexibility of VAR signature sequence.

  • Updated in V73

    Release date
    27 February 2014

    Acrobat PDF/A - Portable Document Format 1b: Additional signature added in order to avoid misidentifying some PDF/A's which contain 1b conformance declaration as PDF's. Research request by Antonio Dalvit and Erica Betto working in an italian project for documentation/configuration management in ASI srl.

  • Updated in V55

    Release date
    4 January 2012

    Acrobat PDF/A - Portable Document Format 1b: Existing signature refined through PRONOM Research.

  • Added in V51

    Release date
    15 July 2011

    Acrobat PDF/A - Portable Document Format 1b: Signature developed through PRONOM Research.

    Acrobat PDF/A - Portable Document Format 1b: Full entry added.