PDF/A is an ISO-standardized version of the "Portable Document Format" (PDF). PDF/A (A = Archiving) is a subset of the PDF options specifically for the requirements of long-term archiving and barrier freedom, and also for reproduction on mobile terminals such as PDAs. The standard of the first release from the year 2005 (PDF/A-1) is a subset of PDF 1.4 and is specified under ISO 19005-1:2005.
By linking to webPDF, n2pdf is also able to access the standards of ISO 19005-2:2011 (PDF/A-2) and ISO 19005-3:2012(PDF/A-3), thereby also benefiting from functions which were added with PDF versions through 1.7. Conformance levels "a," "b," and "u" (for PDF/A-2 and PDF/A-3) are supported.
The respective standards specify several levels of conformance, depending on the version.
Level A conformance
(Accessible) conformance: A PDF file with A-level conformance requires both clear visual reproducibility and the ability to display the text in Unicode as well as content structure of the document.
Level B conformance
(Basic) conformance: A Level B conformant PDF file requires a clear visual reproducibility. The structural or semantic settings of the level need not be retained.
Level U conformance
(Unicode) conformance: A PDF file with level U conformance must fulfill the requirements for a PDF file with level B conformance as well as have correct Unicode semantics for the entire text in the document so that the entire text can be indexed and displayed.
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A key summary statement is that all of the content used, in particular the images and texts (a limitation to the characters used is allowed), must be contained in the file. References to resources which are not a part of the PDF file are not allowed.
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The new standards of PDF/A-2 and PDF/A-3 are only available via web2PDF as of version 4.0. Consequently, when these standards are activated, webPDF is required.
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To create a PDF file which meets the requirements of PDF/A, the option N2PDFOPTION_PDF_PDFA_MODE must be set with the function N2PDFSetOption. The following parameters are available:
N2PDFVALUE_PDFA_NONE |
not PDF/A conformant file |
N2PDFVALUE_PDFA_LEVEL_1A |
PDF/A-1a compliant file |
N2PDFVALUE_PDFA_LEVEL_1B |
PDF/A-1b compliant file |
N2PDFVALUE_PDFA_LEVEL_2A |
PDF/A-2a compliant file |
N2PDFVALUE_PDFA_LEVEL_2B |
PDF/A-2b compliant file |
N2PDFVALUE_PDFA_LEVEL_2U |
PDF/A-2u compliant file |
N2PDFVALUE_PDFA_LEVEL_3A |
PDF/A-3a compliant file |
N2PDFVALUE_PDFA_LEVEL_3B |
PDF/A-3b compliant file |
N2PDFVALUE_PDFA_LEVEL_3U |
PDF/A-3u compliant file |
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Please note that the activation of the PDF/A standards causes some settings in n2pdf to be activated automatically. This relates e.g. to the font embedding or encryption of the file. It can also cause e.g. a marked change to the size of the PDF file. |