Ad error after page exported in PDF

So, we receive an ad from an advertiser in PDF format, place on the page, add our copy around it, and export the entire Quark layout as a PDF. We then send the PDF pages to the printer. When the pages come back, the fonts on the ad were all scrambled, but the background images and other b/w images within that ad, and the rest of the page, were fine. All fonts used in the ad were already in my library, so I am lost. Any thoughts or experiences as to why this would happen?

The original ad was created (God knows why) in CorelDraw on a PC, and saved as a PDF. We got the PDF on our Mac, and exported our pages in Quark. I cannot figure out the problem. This could cost us some big penny. Your thoughts are welcomed.

 

Only thing I could see which might save you is if you can have a techie transfer the needed font "suitcase" from CorelDraw to Quark. Perhaps your set of fonts is corrupted.

 

We have postscript errors to our image setters all the time, basically because some of the guys in our ad services department let this stuff get through.

To avoid getting in trouble (again), I'll end my thoughts here.