PDF import into QuarkXpress

Has anybody else had a problem importing a PDF file into QuarkXpress on a Mac. For some reason the file dosen't hold onto its fonts or pictures, the characters run into each other, and they just look a mess. I put a copy of QuarkXpress onto a PC and the PDF files import with no problems, they are perfect, which leads me to think that its a MAC OSX problem. I have been suffering this problem for some time now, its like have toothache!!!!! Can anybody help me? Please!!!!!!!!