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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/
Release date
01 Oct 2005
Format encoding
Binary
File extensions
pdf
Submitted by
Digital Preservation Department / The National Archives

Relationships

Has lower priority than
Has priority over

Internal signatures

Acrobat PDF/A 1b 1

Description
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.
Provenance
Ongoing DROID research following request from Archaeology Data Service. Signature further refined Nov 2011 with additional EOF sequence in order to avoid misidentifying some PDF/A's which contain 1b conformance declaration, but which are invalid as PDF/A 1b's.

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

Description
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.
Provenance
Ongoing DROID research following request from Antonio Dalvit. Signature further refined Feb 2014 to allow variations in the additional byte sequence order, in order to avoid misidentifying some PDF/A's which contain 1b conformance declaration as PDF's.

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

  • V101

    Release date
    15 February 2022

    • Added signature

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

    • Updated

      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.

  • V89

    Release date
    8 March 2017

    • Updated

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

  • V88

    Release date
    27 September 2016

    • Updated

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

  • V81

    Release date
    18 February 2015

    • Updated

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

  • V74

    Release date
    31 March 2014

    • Updated

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

  • V73

    Release date
    27 February 2014

    • Updated

      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.

  • V55

    Release date
    4 January 2012

    • Updated

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

  • V51

    Release date
    15 July 2011

    • Added format

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

    • Added signature

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