Quit Safari then open the Finder.
From the Finder menu bar top of your screen click Go > Go to Folder
Type this exactly as you see it here:
Click Go then move the PDF Browser plugin (or just Browser plugin) from the Internet Plugin-Ins folder to the Trash.
Relaunch Safari to test.
When I click on downloaded pdf via Safari I get a message: "There was an error in opening this document. The file is damaged and could not be repaired." I have the latest version of Adobe Reader.
This means that I have to go to Firefox to download and read a pdf. This is rather a nuisance.
Thank you, Pat