Adobe Reader X for Windows has the ability to keep a list of the most recent PDF files that you have viewed. Using this feature, you can quickly reopen a file that you viewed previously without searching for the file manually in Windows Explorer. However, this feature lacks one key privacy element in that Adobe Reader X has no function to clear the history. If you need to remove the recent documents that you have viewed in Adobe Reader X, you can do so by removing a key from the Windows registry.
Open the Start menu and type "regedit" in the "Search programs and files" field. Press "Enter" to launch the registry editor application.
Open the "HKEY_CURRENT_USER" folder on the left side of the window.
Open the "Software" folder.
Open the "Adobe" folder.
Open the "Acrobat" folder.
Open the "10.0" folder.
Open the "AVGeneral" folder.
Right-click the "cRecentFiles" folder under the "AVGeneral" folder and select "Delete."
Click "Yes." This clears the recent document history from Adobe Reader X. The next time you run the application, it recreates the "cRecentFiles" registry key and begins tracking the document history again.