Hi @NathanC and @Graphical Chris,
I wanted to add some observations to this issue.
I did some tests yesterday and today and figured out that the overprint option on PDF export seems only to work with PDF-X (PDF-X/4 in my case).
Attached two simple exported files and the Output preview of both in Acrobat Pro with the Black plate turned off:
1. The PDF (Press ready) export:
2. And here the output preview of a PDF-X/4:
The simple AfPub layout file (version 2.4), the PDF export settings and the exported files are also attached.
The sample text is set without defining any special colour swatch with overprint option, but it should export as such with the export option checked.
Best regards
werfox
simple_test_overprint_pressready.pdf
simple_test_overprint_x4.pdf
simple_test_overprint.afpub