A while ago someone noted in this thread an issue with rendering PDFs created by non-Adobe apps. In that case it appeared likely to be a font issue, and was resolved by printing the document to a new PDF. This did leave the question open why Adobe Reader was still capable of displaying the 'non conforming' PDF properly. I've now had my own first experience in 5 years of being unable to read in Preview a PDF that Adobe Reader has no trouble with. The document is from an Australian State Government website and is about 4MB in size. When viewed in Preview it comes up mostly blank (hence a screenshot won't be terribly informative), but there is no apparent problem in Adobe Reader. Unlike with the other problem noted on this forum, printing the document to a new PDF file does not resolve the issue. If I were to hazard a guess as to what was triggering the rendering bug, I'd point to the 'DRAFT' watermark that's been placed on each page. Perhaps this is an issue others have noticed with PDFs created in certain non-Apple, non-Adobe apps?