As per the issue description mentioned above, you want to clear recently printed pdf files history in Acrobat (as shown in the screenshot above) is that correct?
You can clear recent files by locating "remove from recent" in the right hand pane by selecting a file or multiple pdf files under "Recent" tab. However, if you open and print a pdf in Acrobat, it will be visible under "Recent". This behavior is as designed.
Below is a screenshot:
Let us know if you need any further help.