Adobe Reader 9 and Acrobat 9 found to be vulnerable to a 0day exploit where Adobe is planning to release the patches on 11th March 2009:
http://secunia.com/blog/44/
In the first place, the security specialist said that users can be protected by disabling the Javascript on Adobe, which can be found here:
http://www.4shared.com/file/90132463/a01aa640/Adobe_JS_Fix.html
Lately security specialist from Secunia reported that disabling the Javascript cannot eliminate all the risk, more information can be found here:
http://www.adobe.com/support/security/advisories/apsa09-01.html
Conclusion
The only mitigation is avoid opening PDF document from unknown source or cross the finger to wait the 11th March 2009 to reach :)