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).

What can X-PDF-Browser do?

• Embed files into PDF – compressed and optional encrypted
• Extract files back from PDF
• Supports Twofish 256 bit in CBC mode encryption
• the attachments can not been extracted by other programs
• Free for personal and educational use

The program serves as a test bed and demonstrator for implementing new ways of content embedding and encryption modes in PDF.

for details, please visit http://www.wizards.de/~frank/xpdfbrowser.html