Finder generates thumbnail previews for PDF files. The first time I navigate to a folder, it takes a while (1-2 seconds per file) for the thumbnails to appear, but on subsequent visits to the same folder, the thumbnails show up pretty much instantly. Where are the thumbnails stored? (In Windows XP they are stored in a hidden thubms.db file, is there something equivalent in Mac OS X?
Mine was about 500 MB and 100 MB on different installations of OS X.
A similar question at Ask Different: For applications that do not store Quick Look information within the file, where does Lion (or a Server) store that information?