A fill, stroke or stroke gap set to overprint in [Paper] or in a process
colour that lays down no ink (C=0 M=0 Y=0 K=0, gray 0, RGB white, a 0%
tint) disappears on press. Preflight now reports it as whiteOverprint, and
ruby and kenten set to overprint in such a colour too. A spot ink (a white
ink or a varnish) prints whatever colour stands in for it, so it isn't
reported. Text has no overprint of its own, so white text knocks out and
prints, and isn't reported. The old Preflight note that PDF export drops
ruby and kenten overprint is gone: export writes it.