Try doing this with a pdf that you know does not have anything. Create a google sheet or doc with full access and download it as a pdf. Use this pdf in your testing.
Have you tried simply using the Open an external website workflow action with the File’s Url and the ‘Open in a new tab’ checkbox ticked?
The open in a new tab funcationality has been added not too long ago and it makes all these plugins obsolete. They probably should have announced it louder
If that doesn’t work then its probably a problem with permissions.