Okay, before you do the defaults thing in 'Open with', find the file location by typing in the program name into start menu search, right-clicking the program and on the 3rd/4th option down should be 'Open file location'.
Click next to the folder in the address bar (address bar, not an actual file), and press 'Ctrl' + 'C'. Now go to the 'Open with' option on your PP Viewer file, and when you choose the browse option in the set default, click on the address bar and press 'Ctrl' + 'V'.
This copies the location of PP viewer, and now you can use the pp file default opening with the pp file.