I'm updating our marketing gumpf - and I want to be as proper as I can/we should be, and want to write Autodesk® Revit® where we used to simply write Revit... which is easy enough, but a great number of software vendors don't seem to make a point of making clear which superscript appendage to use on their names/their product names.

...and yes, I've tried the "About" page - and again, some just seem to leave them out.

How (if at all) do you stay on top of this in your documentation?

Companies usually have an extensive document on branding guidelines, how & when their branding should be invoked etc, I'd fire off an e-mail and ask for it if I were you.