For PDF/A conversion we rely on ‘pdftron.PDF.PDFA.PDFACompliance’ from PDFTron PDFNet SDK.
The conversion works great, however I would like to be able to add some custom properties / metadata (i.e. extended XMP metadata in a custom namespace ).
a) Load initla XMP metadata from PDF (see How do I embed and extract XMP data associated with a PDF document?).
b) Convert to PDF/A
c) Overwrite the original metadata with your own version (this is also covered in the above article).
The problem is that PDF/A 1 - does not support compressed PDF streams, so failing to use the flag could introduce compatibility issue relared to ‘compressed object streams’