How does PDF/A-1 address long-term preservation needs?
PDF/A is the first in a new family of ISO Standards to address the growing need to maintain information in electronic documents over archival time spans. It has been established as a row of standards with several parts. Currently only PDF/A-1 (Part 1) has been approved. Then how does PDF/A-1 address long-term preservation needs?
PDF/A-1 requires device independent components so that the static visual appearance can be reliably and consistently rendered and printed without regard to the hardware or software platform used. The graphics clause, for example, incorporates requirements to ensure predictable color rendering. PDF/A-1 also prohibits the use of components not defined in PDF Reference 1.4.
Everything that is necessary to render or print a PDF/A-1 file must be contained within the file. The fonts clause requires that all fonts used for rendering content are embedded in the file. A PDF/A-1 conforming writer must always embed fonts, and a conforming reader must always use the embedded fonts. This means that the file will be rendered using the fonts intended and not using fonts residing on the local workstation.
PDF/A-1 requires Adobe Extensible Metadata Platform (XMP) be used for embedding metadata in PDF files. To allow flexibility of implementation, PDF/A-1 provides recommendations for documenting file attributes such as: File identifier, File provenance, Font metadata, and allows non-XMP schemas to be included, as long as they are embedded. Implementers can use XMP in a variety of ways to include information about electronic records within the file itself. Having metadata embedded in the file can increase the informational value of electronic documents and enhance the future researcher’s understanding of the document.
PDF/A-1 prohibits encryption. This prohibition means that User IDs and/or Passwords are not needed to do anything with a PDF/A-1 file. PDF/A-1 files are open and available to anyone or any software that processes the file. Implementers that require access controls can provide these access controls outside of the file format.
PDF/A-1 is based on an authoritative specification that is publicly available. Anyone can use the PDF Reference and XMP Specification in conjunction with PDF/A-1 to create applications that read, write, or process PDF/A-1 files. Adobe has granted a general royalty free license to use certain of its patents to create applications that process PDF/A-1 files. Additionally, Adobe has granted AIIM and NPES the rights to publish these specifications on their respective Internet sites into the indefinite future.
PDF/A-1 was designed for flexibility of implementation to promote its wide adoption. If widely adopted, PDF/A software tools will proliferate, and the market will support the file format as long as the demand exists. Market support of PDF/A will help ensure the viability of PDF/A and extend the length of time that PDF documents can be maintained as PDF/A.