Hi I was able to figure out a method. I am surprised it isn't just as easy as selecting File, then delete. Here goes:
Once you open your .pdf file, in a blank space on the screen RIGHT CLICK. A pop up menu will appear and locate: Document Properties click once on it. Another pop up menu will appear and about 4 lines up from the bottom find: Location: Whatever the description is next to Location, click once on it. It will take you to the file and it will automatically be highlighted blue.
Now here's next steps. You must close out of the original .pdf document and the Document Properties pop up menu (red x in upper right hand screen).
This will leave the Location of that document and it will still be highlighted blue. Just hit your delete key and it will go to the trash on your desktop. It is gone. Don't forget to empty your trash so it is really gone!
Good luck!
