Try Scansoft, er, Nuance's PaperPort software. It's not free or open source (haven't looked for one yet) but it shows thumbnails of a lot of formats including PDF:

http://www.nuance.com/paperport/
"PaperPort simplifies things. It's the best tool available to make your all-in-one device or scanner easier and more efficient to use. It enhances Microsoft Windows with large clear thumbnails of over 150 document and photo formats. Now you can easily print, organize and share all your documents."

I used it a while back to help get more organized and go paperless in the home office. uh it worked for a while but then the paper piled up faster than I could scan and shred it!