Adobe is currently investigating a new security hole in Reader and Acrobat. Cybercriminals are currently spamming emails with prepared documents which lead to an infection of the computer with malware.
Anyhow users are best advised to not open PDF files they receive unexpectedly until Adobe provides Updates for Reader and Acrobat.
This afternoon, Adobe received reports of a vulnerability in Adobe Reader and Acrobat 9.2 and earlier versions being exploited in the wild (CVE-2009-4324). We are currently investigating this issue and assessing the risk to our customers. We will provide an update as soon as we have more information.