Adobe has released a security bulletin for Acrobat detailing an exploit that exists in malicious PDF documents.  While Adobe has had knowledge of this exploit since December 15th, a hotfix will not be deployed until January 12th.

It is recommended to disable Javascript, or if you’re using Firefox, disable the PDF plugin under Tools -> Add-ons -> Plugins until the hotfix is released.  If you choose not to do these things, ensure that you only open PDF files from sites you trust, and certainly don’t open any that randomly pop up on screen, as they are most likely triggered by targeted banner ads containing virus laden code.

Full Report: Security Advisory for Adobe Reader and Acrobat