I have had instances where I needed to use Creo within PDM Pro - we did not have or use the add-in. It is fairly simple but you need to make sure you have the latest version and do check-in / out through file explorer.
Even this manual process it was still easier to deal with than Windchill IMO
I would assume the add-in would allow an interface to handle getting the latest, checking in and out, and handling where used and conatins.
Have you contacted your VAR?