I like use Sumatra PDF, because it is a slim, free, open-source PDF reader for Windows. Portable out of the box. and I just notice it has updated to 1.3 on Feb 04, 2011 with many changes,

* improved text selection and copying. We now mimic the way a browser or Adobe Reader works: just select text with mouse and use Ctrl-C to copy it to a clipboard
* Shift+Left Mouse now scrolls the document, Ctrl+Left mouse still creates a rectangular selection (for copying images)
* ‘c’ shortcut toggles continuous mode
* ‘+’ / ‘*’ on the numeric keyboard now do zoom and rotation
* added toolbar icons for Fit Page and Fit Width and updated the look of toolbar icons
* add support for back/forward mouse buttons for back/forward navigation
* 1.2 introduces a new full screen mode and made it the default full screen mode. Old mode was still available but not easily discoverable. We’ve added View/Presentation menu item for new full screen mode and View/Fullscreen menu item for the old full screen mode, to make it more discoverable
* new, improved installer
* improved zoom performance (zooming to 6400% no longer crashes)
* text find uses less memory
* further printing improvements
* translation updates
* updated to latest mupdf for misc bugfixes and improvements
* use libjpeg-turbo library instead of libjpeg, for faster decoding of some PDFs
* updated openjpeg library to version 1.4 and freetype to version 2.4.4
* fixed 2 integer overflows reported by Stefan Cornelius from Secunia Research

My Batch ReaderEnable software supports batch convert PDF files with one of the following features,

• Enable For Commenting and Analysis In Adobe Reader(aka Reader Enable and called “Enable Commenting & Measuring…” in Adobe Acrobat X Pro)
• Enable TypeWriter Tool in Adobe Reader(aka TypeWriter Enable, called “Enable Adding Text in Document (that are not fillable forms)…” in Adobe Acrobat X Pro
• Enable usage rights for Adobe Reader (aka Usage Rights Enable called “Enable Additional Features…” in Adobe Acrobat X Pro)

btw, Batch ReaderEnable has three editions,

• GUI Version(Window Version)
• Console Version
• Hotfolder Automation/File Monitor/Folder monitor Version, automatically monitor the selected folder(with sub-folder) and convert the new PDF files in the folder

• If want to buy GUI Version and Console Version, please click here, and If you want to Buy Hotfolder version, please visit here.

On June 17, 2010,

Chromium’s blog announced that the latest Google Chrome dev build for Windows and Mac includes a plug-in for viewing PDF files. The plug-in can be enabled by going to chrome://plugins/ and clicking on “Enable” for the “Chrome PDF Viewer” plug-in.

and On February 17, 2011, Google OS said,

If you use Google Chrome and you haven’t disabled the built-in PDF plugin, you can now open PDF attachments from Gmail using your browser’s viewer. Just click “View” next to the attachment and you’ll notice that the PDF file opens faster and it looks much better.

The Chrome PDF plug-in is faster than the Google Docs previewer, its rendering accuracy is better, and you don’t have to change settings anywhere for this to take effect. Just use Gmail in Google Chrome and the ‘view’ link will automatically open your file in the Chrome PDF viewer.
The change is also nice because Chrome’s PDF plug-in actually lets you print, unlike the previewer which can only manage recursion printing (it generates a PDF of your PDF).