I have tested this on a range of colour profiles and in RGB/8 and RBG/16. Colours export fine to PDF without any opaque objects on the page, but as soon as I add a shape with even the slightest bit of opacity to the page, all colours get massively dulled in the PDF that is exported.
Tried changing to a range of different PDF export settings, and made sure that colour space is set to use the Document Profile (Embed profiles is ticked too).
"Flatten" is the only export preset that doesn't cause this issue, but I need to retain editability of the PDF.
Sample 1.pdf shows a turquoise rectangle with no opacity (all colours are correct), Sample 2.pdfshows the results when I lower the opacity of the turquoise rectangle (dull). Please download PDFs and open in Adobe Acrobat to see the differences (colour differences don't show in browser).
Using an iMac (Retina 5K, 27-inch, 2017) running Catalina 10.15.7
After switching from Adobe I'm loving AP and AD so far, please don't make me go back to Adobe! PLEASE I BEG YOU!!!