I've been having intermittent problems with the Preview app showing PDF files with either missing text or distorted fonts. The PDFs all display correctly if I use Adobe Acrobat (Reader or Professional). The one I can consistently get to malfunction is the PDF generated by the Postal Service label generator. The barcode always prints incorrectly by Preview, yet if i pull up that very same file in Adobe, it displays and prints just fine. Any ideas on what could be wrong?