There is a very simple - almost too easy - way to get the PC-300 running under ANY platform:
Forget USB and use MIDI! 🙂
Okay, you need a MIDI interface or a soundcard with a MIDI connection. In my case it's the Komplete Audio 6 USB device which has a MIDI output.
I consider this to be the ideal solution which is future proof. You just don't have to mess around with old drivers or depend on the manufacturer to release new ones.
It's as simple as that - hope this helps!
Cheers
P.S.: The linked drivers mentioned before are for the PCR-300 which is a completely different device. They are not working with the PC-300.