Sumatra PDF is a slim, free, open-source PDF reader for Windows. Portable out of the box.

Changelog:
* browser plugin for Firefox/Chrome/Opera (Internet Explorer is not supported). It's not installed by default so you have to check the apropriate checkbox in the installer
* IFilter that enables full-text search of PDF files in Windows Desktop Search (i.e. search from Windows Vista/7's Start Menu). Also not installed by default
* scrolling with right mouse button
* you can choose a custom installation directory in the intstaller
* menu items for re-opening current document in Foxit and PDF-XChange (if they're installed)
* we no longer compress the installer executable with mpress. It caused some anti-virus programs to falsely report Sumatra as a virus. The downside is that the binaries on disk are now bigger. Note: we still compress the portable .zip version
* -title cmd-line option was removed
* support for AES-256 encrypted PDF documents
* fixed an integer overflow reported by Jeroen van der Gun and and other small fixes and improvements to PDF handling

Program Information Category: Tools and Utilities Type: Free Version: 1.4 Size: 4.12MB Works on: Windows Product page: here