This release is today 29 Apr 09:
Adobe has acknowledged a security vulnerability in the newer readers (8.1.4 & 9.1) which may allow execution of arbitrary code with the privileges of the user running the application.
The Linux versions definitely have the bug and other platforms that Adobe provides readers PC and Mac may also be at risk.
For its part, Adobe's acknowledgement was brief. "Adobe is aware of reports of a potential vulnerability in Adobe Reader 9.1 and 8.1.4," said David Lenoe, the company's security program manager, in a security blog entry. "We are currently investigating, and will have an update once we get more information."