Following on from yesterday's post I just came across this very useful source of information on PDF/A: the PDF/A Conformance Center. This provides links to resources such as this whitepaper PDF/A - A new Standard for Long-Term Archiving, and a number of technical notes, especially Metadata and PDF/A-1(also available as a PDF). (This latter corrects some errors in the ISO standard which are to be redressed in a forthcoming Technical Corrigendum later this year.)

The site also links to the standard, to a FAQ, to PDF/A products and to news and events. There's also an RSS feed and a discussion forum.

Still difficult to find examples of PDF/A though (the discussion forum doesn't throw up too much on that score) although at least the Technical Note linked to above is a PDF/A-1 document as can be seen from this XMP description:

      <rdf:Description rdf:about=""
            xmlns:pdfaid="http://www.aiim.org/pdfa/ns/id/">
         <pdfaid:part>1</pdfaid:part>
         <pdfaid:conformance>A</pdfaid:conformance>
      </rdf:Description>
 

As noted before, PDF/A may be more (and less) than CrossRef publishers require at this time, but nonetheless it is certainly a useful yardstick as regards embedding metadata within a PDF and is anyway a technology worth tracking in its own right.