Users should be cautious when processing PDF documents, keep AV signatures updated, and be on the lookout for patches that are forthcoming

Adobe Reader – Patch being developed for new zero-day attack
http://www.adobe.com/support/security/advisories/apsa11-04.html

QUOTE: A critical vulnerability has been identified in Adobe Reader X (10.1.1) and earlier versions for Windows and Macintosh, Adobe Reader 9.4.6 and earlier 9.x versions for UNIX, and Adobe Acrobat X (10.1.1) and earlier versions for Windows and Macintosh. This vulnerability (CVE-2011-2462) could cause a crash and potentially allow an attacker to take control of the affected system. There are reports that the vulnerability is being actively exploited in limited, targeted attacks in the wild against Adobe Reader 9.x on Windows.

We are in the process of finalizing a fix for the issue and expect to make available an update for Adobe Reader 9.x and Acrobat 9.x for Windows no later than the week of December 12, 2011. Because Adobe Reader X Protected Mode and Adobe Acrobat X Protected View would prevent an exploit of this kind from executing, we are currently planning to address this issue in Adobe Reader X and Acrobat X for Windows with the next quarterly security update for Adobe Reader and Acrobat, currently scheduled for January 10, 2012. We are planning to address this issue in Adobe Reader and Acrobat X and earlier versions for Macintosh as part of the next quarterly update scheduled for January 10, 2012.