For each PDF/A-1 validation issue we try to explain what it means and, if possible how to resolve it. For a more technical explanation of the issue we quote the related section of the ISO 19005-1 PDF/A Specification.
PDF/A-1 imposes certain requirements and restrictions on document metadata in a compliant PDF/A-1 file where certain information is required to be encoded as XMP metadata, while corresponding entries in the document information dictionary for a document may be present but must match information present in the document’s XMP-encoded metadata.
For more information go to the PDF Association website and from the Publications page, search for the relevant Technical Note publication.