Writing XMP metadata to PDF breaks PDF/A specification

[ww23]

After modifying the XMP metadata of a PDF/A-3b file with

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exiftool -XMP-pdf:Producer="Producer" Test.pdfthe preflight in Adobe Acrobat complains that the document doesn't conform to PDF/A-3b.
The original file was ok.
How can I modify XMP metadata while still preserving the PDF/A-3b standard?

Maybe this is relevant:

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Producer
If the Producer entry (of PDF data type text string) is present in the document information dictionary, the document's Metadata must contain an equivalent en- try pdf:Producer of XMP data type AgentName where pdf refers to the Adobe PDF schema (the prefix is actually arbitrary).(Link)

[Phil Harvey]

Your reference is not relevant since you are writing XMP:Producer and not PDF:Producer.

I suspect that the PDF/A-3b verifier may not like a PDF with an incremental update (although I can't verify this with a quick Google search), or possibly the PDF needs to be linearized.  Either way, you would have to run qpdf (or some other utility) to linearize the PDF and combine the incremental update after writing with ExifTool.

- Phil

[StarGeek]

I suspect that the PDF/A-3b verifier may not like a PDF with an incremental update (although I can't verify this with a quick Google search)

I did a more extensive google search when this question first popped up and couldn't verify it either.

Here's a page which describes the incremental update procedure.