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|Type code||'PDF ' (including a single space)|
|This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (March 2013)|
|Type code||'PDF ' (including a single space)|
PDF/A differs from PDF by omitting features ill-suited to long-term archiving, such as font linking (as opposed to font embedding). (Similarly, the PDF/X file format is specially adapted to digital printing and graphic arts.)
Removing PDF/A for editing. In Adobe Acrobat select Edit - Preferences - Under Categories column select Documents on the Right go down to PDF/A View Mode - in check box select - Never.
PDF/A is designed to give a minimal feature set to enable long term storage assuming that storage formats will vary in future rendering a full PDF document either partially or totally unreadable.
PDF/A-1 is based on the PDF Reference Version 1.4 from Adobe Systems Inc. (implemented in Adobe Acrobat 5 and later versions) and is defined by ISO 19005-1:2005, an ISO Standard that was published on October 1, 2005: Document Management – Electronic document file format for long term preservation – Part 1: Use of PDF 1.4 (PDF/A-1)
PDF/A-2 is based on ISO 32000-1 – PDF 1.7 and is defined by ISO 19005-2:2011, published on June 20, 2011 under the formal name Document management – Electronic document file format for long-term preservation – Part 2: Use of ISO 32000-1 (PDF/A-2). PDF/A-2 is a very recent standard and is not widely used.
PDF/A-3 is based on ISO 32000-1 – PDF 1.7 and is defined by ISO 19005-3:2012, published on October 15, 2012 under the formal name Document management -- Electronic document file format for long-term preservation -- Part 3: Use of ISO 32000-1 with support for embedded files (PDF/A-3).
|Part||Name||Formal name||Release date||Standard||Based on PDF version|
|Part 1||PDF/A-1||Use of PDF 1.4 (PDF/A-1)||2005||ISO 19005-1||PDF 1.4 (Adobe Systems, PDF Reference third edition, 2001)|
|Part 2||PDF/A-2||Use of ISO 32000-1 (PDF/A-2)||2011||ISO 19005-2||PDF 1.7 (ISO 32000-1:2008)|
|Part 3||PDF/A-3||Use of ISO 32000-1 with support for embedded files (PDF/A-3)||2012||ISO 19005-3||PDF 1.7 (ISO 32000-1:2008)|
PDF is a standard for encoding documents in an "as printed" form that is portable between systems and is widely used for distribution and archiving of documents. However, the suitability of a PDF file for archival preservation depends on options chosen when the PDF is created: most notably, whether to embed the necessary fonts for rendering the document; whether to use encryption; and whether to preserve additional information from the original document beyond what is needed to print it.
PDF/A was originally a new joint activity between The Association for Suppliers of Printing, Publishing and Converting Technologies (NPES) and the Association for Information and Image Management, to develop an International standard to define the use of the Portable Document Format (PDF) for archiving and preserving documents. The goal was to address the growing need to electronically archive documents in a way that would ensure preservation of their contents over an extended period of time, and would further ensure that those documents would be able to be retrieved and rendered with a consistent and predictable result in the future. This need exists in a growing number of international government and industry segments, including legal systems, libraries, newspapers, and regulated industries.
The Standard does not define an archiving strategy or the goals of an archiving system. It identifies a "profile" for electronic documents that ensures the documents can be reproduced exactly the same way in years to come. A key element to this reproducibility is the requirement for PDF/A documents to be 100% self-contained. All of the information necessary for displaying the document in the same manner every time is embedded in the file. This includes, but is not limited to, all content (text, raster images and vector graphics), fonts, and color information. A PDF/A document is not permitted to be reliant on information from external sources (e.g. font programs and data streams), but is permitted to include annotations (e.g. hypertext links) that link to external documents.
The standard specifies two levels of compliance for PDF files:
PDF/A-1b has the objective of ensuring reliable reproduction of the visual appearance of the document.
PDF/A-1a includes all the requirements of PDF/A-1b and additionally requires:
PDF/A-1a objective is to ensure that document content can be searched and repurposed.
The requirements for Level A conformance place greater responsibilities on writers preparing conforming files, but these requirements allow for a higher level of document preservation service and confidence over time. Level A conformance also facilitates the accessibility of conforming files for physically impaired users.
According to the specification, the following terms are recommended when referring to the ISO 19005-1:2005 specification when the full ISO name is not being used:
PDF/A-2 is the second part to the standard. PDF/A-2 address some of the new features added with versions 1.5, 1.6 and 1.7 of the PDF Reference. PDF/A-2 should be backwards compatible, i.e. all valid PDF/A-1 documents should also be compliant with PDF/A-2. However PDF/A-2 compliant files will not necessarily be PDF/A-1 compliant.
Part 2 of the PDF/A Standard is based on a more recent version, PDF 1.7 (ISO 32000-1), rather than PDF 1.4 and offers a number of new features:
Part 2 defines three conformance levels: PDF/A-2a, PDF/A-2b and a new conformance level PDF/A-2u. PDF/A-2u represents Level B conformance (PDF/A-2b) with the additional requirement that all text in the document have Unicode mapping.
PDF/A-3 (ISO 19005-3:2012. Part 3) allows embedding of arbitrary file formats (such as XML, CSV, CAD, wordprocessing documents, spreadsheet documents and others) into PDF/A as complete archived objects.
The PDF/A-3 specification was published on October 17, 2012.
A PDF/A document can be identified as such through PDF/A-specific metadata located in the "http://www.aiim.org/pdfa/ns/id/" namespace. However, claiming to be PDF/A and being so are not necessarily the same :
The PDF/A specification also states some requirements for a conforming PDF/A reader, which must
Some PDF viewers, e.g., Adobe Reader 9, will by default switch into a special "PDF/A viewing mode" to fulfill these requirements whenever a document declares in its metadata that it is PDF/A compliant. This may also alert the user that this mode has been activated, and disable functions for changing the document.
As a PDF/A document must embed all fonts that it uses, a PDF/A file will often be bigger than an equivalent PDF file that does not have the fonts embedded.
The use of transparency is forbidden in PDF/A-1. The majority of PDF generation tools that allow for PDF/A document compliance, such as the PDF export in OpenOffice.org or PDF export tool in Microsoft Office 2007 suites, will also make any transparent images in a given document non-transparent. That restriction was removed in PDF/A-2.