According to this article there is a security hole in Adobe Reader that can be exploited to allow someone to execute code on your machine. The problem affects all versions of Adobe reader including 8.1.4, 9.1, 7.11 and earlier and Windows, Mac and Unix platforms can all be affected. Security experts are recommending that people disable Javascript in the application to help reduce the risk of the hole being exploited. You can disable JavaScript from the General Preferences dialog box but unchecking the Enable JavaScript function under the Edit Preferences option.