Adobe Reader provides users with the option to reduce the number of recently opened files. This is a quite useful feature when you are working on a system which is shared with other users. And you do not want others to know the files that you had accessed in Adobe Reader. Unfortunately you do not have an option to completely clear the recently accessed files history. The default number of recently opened files displayed is 5.
Adobe Reader users can access the recently opened files by clicking File menu -> Open Recent File. If you want to see all the recently accessed documents then click View All Recent Files option.
Reduce the number of recently accessed files in Adobe Reader on Mac
Click Adobe Reader menu and Select Preferences from the listed menus.
In the Preferences screen, click Documents tab and navigate to Open Settings.
Set the value for “Documents in recently used list” to 1. Then click OK button to save and close the Adobe Reader Preferences screen. Open Recent Files menu on Adobe Reader should display only one document.