PDF/A is one set of standards among a suite of PDF-based standards managed by the International Organization for Standardization (ISO). It was developed to enable the long-term preservation of electronic documents and provides specifications for the creation, viewing, and printing of PDF documents, with the intent of preserving final documents of record as self-contained documents.
The standard does not define an archiving strategy or the goals of an archiving system. Rather, it identifies a "profile" for a PDF file that makes it possible to reproduce the visual appearance of the document the exact same way in the future. This profile specifies what must be included in the file, while prohibiting features that are not suitable for long-term archiving.
The current version of the standard is PDF/A-1 and is based on PDF v1.4. The next generation, PDF/A-2, is under development and will add selected features from the newer "umbrella" or master PDF standard, ISO-32000-1, which is now maintained by ISO.
Key characteristics of a PDF/A file
|Self-documenting||PDF/A promotes the use of metadata, enhancing the document by providing information about the document itself. It provides recommendations, for instance, for documenting file attributes such as file identifier, file provenance, and font metadata. When metadata is used, PDF/A requires the use of the Extensible Metadata Platform (XMP) for embedding the data in the files.|
|Device independent||PDF/A requires device-independent components, such as specific RGB or CMYK color profiles, so that the static visual appearance can be reliably and consistently rendered and printed without regard to the hardware or software platform used.|
|Unfettered||PDF/A prohibits encryption so that a compliant PDF/A file must be open and available to anyone or any software that processes the file. User IDs and/or passwords cannot be embedded. Access control is typically managed outside the file format by a content or records management system. Live digital signatures can be included in a PDF/A file as long as they are applied after the PDF/A file has been created. To make sure the file remains compliant with the standard, be sure to apply the signature using software that is PDF/A aware.|
|Two levels of compliance||There are two levels of compliance. The lowest level, PDF/A-1b, meets all the core requirements, helping to ensure reliable reproduction of the visual appearance of a document. This specification is often applied to scanned images and preexisting PDF files that are converted to PDF/A. The higher level, PDF/A-1a, requires a document structure called "tags" that provides an underlying structure for the content within the document and facilitates searching, repurposing of content, and accessibility for people with disabilities such as blindness. This higher level specification is typically applied to "digitally born" documents captured directly from applications like Microsoft Word that create document structure during the authoring process.|