Open PDF in Papers 3

Using hook & Papers3, the linked pdf is opened in preview, not in papers3. Modifying the Get Address AppleScript seems to solve it:

tell application “Papers”
set p to selected publications of front library window
set n to count of p
if n = 1 then
set aurl to item url of first item of p
end if
end tell

Hook is designed such that a file type (MIME type, based on file extension) is opened in accordance with the macOS user’s preferences. We considered overriding that, but we decided against it for simplicity and >99% of the time in our experience, the user’s macOS configurations are what the user requires.

So if you select the file in Finder and do “Always open with > Papers 3” that should do the trick.

However, it’s great that you were able to use the Script Editor to get the behavior you desired!