Previewing files and attachments in Microsoft Outlook 2007 is one of the new killer features that makes my, and hopefully yours, life easier. When installing Outlook 2007 you will get preview functionality for the standard Microsoft applications and images. Previewing files is also integrated into the Windows Vista Explorer.
Tim Heuer (mr double-snake error) has together with Foxit software created a PDF previewer. The PDF Preview Handler is easy to set up and is incredible fast in rendering PDF documents for preview.
Go get it!