PDF/A

PDF / A is a format for long-term archiving of digital documents, which has been standardized by the International Organization for Standardization (ISO) as a subset of the Portable Document Format ( PDF). The standard specifies how the elements of the underlying PDF versions must be used with regard to the long-term archiving. There are both mandatory and non- approved ingredients.

PDF/A-1

The standard was established in 2005 as ISO 19005-1:2005, Document management - Part 1 - Electronic document file format for long -term preservation: published Use of PDF 1.4 ( PDF/A-1 ) and specifies two levels of conformance:

  • PDF/A-1b - Level B ( Basic) compliance: exact visual reproduction
  • PDF/A-1a - Level A ( Accessible ) compliance: in exact visual reproduction as well as mapping text to Unicode and structuring of the document so that it can be read in terms of the accessibility of a screen reader.
  • PDF/A-1 based on PDF 1.4.
  • Properties of PDF/A-1b: Not allowed are references to resources that are not included in the file itself, which means in particular that all images and fonts used ( the limit of the characters used is allowed) must be included in the file.
  • Colors must be sufficiently defined to ensure a unique color representation. Here either source profiles or "Output Intent" come ( description of the typical type of output using an ICC profile, such as sRGB for screen-based documents) to the application.
  • Transparent elements are not allowed.
  • The use of JavaScript or actions are not allowed because their execution could change or influence the content or presentation of the PDFs. Audio or video data can not be embedded.
  • Encryptions and thus partially blocking functions such as printing and file data copy is prohibited.
  • The use of proprietary components, in particular the compression by means of Lempel -Ziv -Welch algorithm ( LZW ) is prohibited. Although it can be assumed that the LZW compression algorithm is now more burdened with any patent, was by the ISO but for safety reasons the use of LZW excluded - not least because ZIP is an equal compression available that is free of patents.
  • Properties of PDF/A-1a, in addition to the properties of PDF/A-1b: All text must be able to be mapped to Unicode.
  • The content structure of the PDF / A file must be specified using tagged PDF.

PDF/A-2

The standard was on 20 June 2011 and ISO 19005-2:2011, Document management - Part 2 - Electronic document file format for long -term preservation: Use of ISO 32000-1 ( PDF/A-2 ) and has defined three levels of conformance:

  • PDF/A-2a: fully realized all the requirements of ISO 19005-2, and in particular all the structural and semantic properties.
  • PDF/A-2b: Minimum requirement of a PDF/A-2 file, guarantees the correct appearance of the document for long-term archiving.
  • PDF/A-2u: as 2b, plus: all text is displayed in Unicode so that all the text can be indexed and displayed.
  • Key enhancements over PDF/A-1: based on PDF 1.7 ( ISO 32000-1 )
  • JPEG 2000 compression allows
  • Transparent elements are allowed
  • Permitted levels
  • OpenType fonts can be embedded
  • Digital signatures in accordance with the PAdES (PDF Advanced Electronic Signatures, ETSI TS 102 778 )
  • Container: PDF/A-1 files can be embedded in PDF/A-2 files

PDF/A-3

The specification of PDF/A-3 was published on 17 October 2012.

Validity

PDF/A-1 shall continue in effect. PDF/A-1-konforme files also meet the requirements of the corresponding PDF/A-2-Konformitätslevels. Where PDF/A-1-Funktionen enough, there is no compelling reason to switch to PDF/A-2.

Review

A validation of valid PDF / A is appropriate inspection tools (see links).

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