I have recently had issues with converting PDFs with spot colours to CMYK pdfs for print. The pdf in question was supplied to us as a multi-page pdf, all vector artwork, built in CMYK with a few spots. However, when converting the document to CMYK (GRACoL2006_Coated1v2), this area of the pdf has not been converting properly. HOWEVER, this is only occurring on half of the pages, the other half are converting correctly.
Original PDF colours (CMYK black (100%K), CMYK purple, and PMS 165)
First Conversion Attempt
Second Conversion Attempt
Third Conversion Attempt
Fourth Conversion Attempt
We tried a few other settings to see if they would work, but our best guess is that some of the pages have different embedded profiles, but we cannot find any tagged elements in the pdf to confirm. Again, only half the pages are doing this, the others are fine but we can't find any difference between them.
We would like to be able to tell our clients how to avoid this when they submit files, but we have no idea how they did it in the first place. Does anyone have any insight?
Hard to answer without having a look at at least two pages (one that works vs. one that does not).