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Processing PDF/A Documents

Special care must be taken when processing PDF/A documents in order to maintain standard conformance. Even simple operations may spoil a document’s conformance status. It is therefore crucial to deploy only tools which are PDF/A-aware to guard against the risk that PDF/A documents are modified in a way which violates the standard.

Splitting and Merging

Even simple operations may result in non-conforming documents. For example, inserting a page in a PDF/A document poses some immediate dangers:

If the inserted page stems from a non-PDF/A document, it may use unembedded fonts.

Even if the imported page stems from a PDF/A document dangers lurk in multiple areas. For example, the color characteristics (e.g. output intent) of both documents don’t necessarily match, which again could result in non-conforming output.

A small operation such as adding a metadata field may violate the standard unless the software properly implements the rules for XMP metadata as mandated by PDF/A.

Any kind of content or metadata processing applied to PDF/A documents must be applied with PDF/Aaware software to avoid jeopardizing PDF/A conformance.

Digital Signatures

Digital signatures in PDF documents can be used to check the document’s integrity, authenticate the person who created the signature, and determine the date and time of signature. Integrated digital signatures are part of PDF 1.4 and are allowed in PDF/A. Multiple document signatures using PDF’s incremental update feature are also allowed. However, the signatures must meet certain requirements for PDF/A:

If the signature has a visual appearance (e.g. an image or a textual representation of the signer’s name) this appearance must meet the same PDF/A requirements as other document parts (deviceindependent color, fonts embedded, etc.).

PDF/A-2 additionally contains requirements regarding the technical details of the signature. The standard also recommends to include timestamping and certificate revocation information in the signature.

The signing procedure should be recorded in the document’s XMP metadata.

In order to make use of digital signatures in PDF/A workflows the signature tool must be aware of PDF/A, i.e. observe the rules outlined above.

The bottom line is that only PDF/A-aware tools must be used in PDF/A workflows; otherwise PDF/A conformance may be spoiled. In order to avoid PDF/A violations through accidental modification Adobe Acrobat opens PDF/A documents in read-only mode by default.