January 2013 Security advisory
http://www.adobe.com/support/security/bulletins/apsb13-02.html

Adds much in the way of new functionality, especially relating to highlighting and commenting, security, and enhanced user experience. Specific new features include the ability to:

- View and interact with PDF files that contain an even wider variety of content types, including drawings, email messages, spreadsheets, videos, and other multimedia elements.

- Make notes and share your feedback with others by marking up PDF documents using the Sticky Notes and Highlighter tools.

- Choose reading mode to fit more content on the screen or two-up mode to view page spreads. Use keyboard shortcuts like print, zoom, and find within the browser.

- Take advantage of the added security of Protected Mode in Reader, which helps ensure safer viewing of PDF files.

- Directly access online services at Acrobat.com from within Reader X. Perform common tasks such as creating PDF files, securely sharing and storing documents, and screen-sharing.

- Expanded PDF access via mobile devices with free Adobe Reader for Android, Windows Phone 7 and Blackberry Tablet OS.