Advanced > Overprint: Preserve (the default; document.exportPdf
advanced.overprint) writes each overprinting fill and stroke (an object's
own, a character's, a type object's) with a graphics state of /OP true
/op true /OPM 1 (/OPM 0 in PDF/A); Discard writes none. White ones knock out
when Document Setup's Discard White Overprint is on, as in print. Mask art
never overprints. File > Print's composite PDF honours Print > Advanced >
Overprints: Preserve the same way (separations keep multiplying plates).
Each overprinting fill or stroke is drawn as a form marked to overprint
(crates/pdf/src/forms.rs); after writing, its content starts by setting the
overprinting graphics state, and the PDF/X self-check runs on the result.
The engine's "overprint is not written to PDF yet" warning and print's
"overprints print as knockouts in composite output" warning are gone.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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