Nemám to doma, ale píšou:
http://forums.techguy.org/all-other-software/56264 3-how-i-clear-opened-files.htmlIn Adobe Reader - Edit - Preferences - select Documents in the left panel and change the "Documents in recently used list" to 1.
It does not allow it to be set to 0 or disabled to my knowledge.
http://forums.adobe.com/thread/887281