You can get the PDF for free on DriveThru RPG.
It’s a generic system, but includes a few settings you can use.
I ran a quick one shot of the Doorway to Infinity setting (it’s free at the Mini Six page linked above). It’s basically a reskinned Doctor Who universe, with a magic doorway in place of a TARDIS.
Here’s a PDF of the pregenerated characters I created for anyone who wants them:
For the scenario I used the TimeWatch adventure, Font of Knowledge that Pelgrane Press put out for Free RPG Day 2017 (free at the link). It’s designed to be used with their TimeWatch RPG setting, but works with only small changes in the Door to Infinity setting.