tl;dr: In Scrivener v3.2.2, on Mac OSX 11.1, using Compile->Print generates a PDF that still has transparent layers. This PDF is acceptable to Amazon KDP, but fails PDF validation when publishing on Ingram.
I understand that Compile->PDF would make sense to keep layers in the generated PDF. However, I think any PDF-for-printing generated with Compile->Print should have all layers, transparencies, etc resolved. While I have published a workaround, this is an extra manual step for people publishing physical books on Ingram. Can Scrivener “Compile->Print” be changed to generate PDFs that are “PDF/A” format? (I do not think there is a need to change how “Compile->PDF” works.)
For full details of the steps-to-reproduce the problem, details of the error message, as well as steps to workaround (converting PDF → PDF/A) that worked for my own book, see thread: https://www.literatureandlatte.com/forum/viewtopic.php?f=2&t=65061.
Hope all that makes sense, but let me know if you have questions or want other details?
Thank you!
John.