I have a few PDF files that render some of the pages (complex line art) VERY slowly. Here is an example: https://www.dropbox.com/s/ph171hsj4pcoyxc/Problem PDF page.pdf It even causes the Dropbox/Safari PDF viewer to hang! Interestingly, if you download and open the file in Preview but shrink the window so that the page is slightly smaller than the "Open at actual size", the rendering becomes instant. For some reason, going at least to 100% size causes one of the processor cores to get pegged at 100% for a few seconds while the images get drawn. The same does not happen when using Acrobat (but the software is otherwise not nice to use). I have other software (Sente) that uses the Preview rendering engine, so it is also slow. This is on 10.6.8 on a quad core mini i7. Anyone else see the same problem in Lion and above?