In Preview>Preferences>PDF tab, is Greeking Threshold ste, and/or Anti-Alias text & Line art? Images Tab... Actual size, Respect DPI?
If you want to Print better Rez, dont print from Safari, but download it, load it in Preview, don't save it, it'll go to 72-150 DPI, just Print from there... any diff?
To save PDFs in better resolution from Preview, try these Quartz Filters courtesy Jerome Colas...
http://discussions.apple.com/thread.jspa?messageID=6250289�