I am trying to export a PDF and need it to be flattened. I went to export it by File > Export as PDF… and the only options I can see are PDF/A-1b, A-2b, and A-3b. I read that A-1a doesn’t support transparency, but that option doesn’t seem to be available. I am using version 7.1
But in 7.1 there is PDF/UA which supersedes PDF/A-1a from what I understand at Accessibility: What PDF/A-1a Really Means – PDF Association
“What’s lacking is a technical description of PDF/A-1a’s true intent; the preservation of not only a visually reproducible document, but an accessible one as well. This description is the subject of another ISO standard – PDF/UA - which we’ll discuss shortly.”
PDF/UA was accepted as an archival format by the US Library of Congress in 2012 according to Wikipedia
Thank you, LO 6.2.8.2 worked!
Note that 6.2’s “PDF/A-1a” is the same as later “PDF/A-1b”. It was removed from the page in commit https://gerrit.libreoffice.org/c/core/+/69294, and soon restored with a different name in https://gerrit.libreoffice.org/c/core/+/74941, using the same code introduced for #i59651 in 2007. It was reported both “conforming” and “non-conforming” to the spec using different validators, and ultimately the decision regarding rename was that “pdf/a-1 enables the basic archival features; if the user wants accessibility features on top, tagged pdf and/or pdf/ua needs to be enabled”. It doesn’t mean that 6.2 supports -1a better.