There is an option for paying the $50 PRTD fee online via CIC payment portal but you need to register an account. You can also make a payment in Euros to 'Bank Austria' and include the receipt with the application. If you hold an Austrian passport then you are visitor visa exempt and don't need the PRTD. Board your flight as normal (agent will assume you are a tourist) and deal with CBSA when your each Canada as a PR.
Travel document (overseas only) R315
Client must obtain this at a mission. It is issued to a PR who needs to travel to Canada and is not in possession of a permanent resident card. Reference: A31(3)