Vulnerabilties in Adobe Acrobat Reader are a common attack point for malware and various exploits. According to the Adobe Acrobat blog, the latest version, Reader X, boasts a significant security enhancement as well as a long list of improvements for Android users.
A new "Protected Mode" in Reader is enabled by default and designed make viewing PDF files less risky by isolating Reader write calls, thus restricting the app's ability to make changes to the Windows file system and registry. Further reading on this protected mode can be found on Adobe's security blog.
In addition to enhanced security, Reader X incorporates support for various multimedia elements, including videos. The Android version offers a bevy of improvements, such as "support for Tablets, go to page, search, opening Portfolios and password protected PDF files, and sharing PDF files via email."
Now is a good time for Adobe to start paying more attention to security, as Google recently integrated a lightweight PDF viewer into its Chrome browser. While the real test for Adobe will be addressing inevitable security holes when they do appear, better security right out of the box is a step in the right direction.