The one caveat being that the card must have been printed as a common in one of the sets that is legal for the format you are playing in. Rancor, for example, is legal in the MTGO and Eternal Pauper formats but not for Modern or Standard Pauper formats.
I run Standard Pauper events at the LGS and this occasionally causes confusion.
Note also that cards printed at common are only legal on MTGO Pauper if they were released online at common. Cards like Hymn to Tourach and High Tide were common in Fallen Empires, but they were only released online at uncommon (in the Masters Edition sets as Fallen Empires was not released online), so they are NOT legal for Pauper on MTGO. They would be legal for paper Pauper.
Currently playing:
UW Modern Tron WU
UR Modern Storm RU
UW [CARD]Rasputin Dreamweaver
[/CARD] UW
I run Standard Pauper events at the LGS and this occasionally causes confusion.
I don't always post about Rafiq of the Many, but when I do, I cardlink to the original artwork, and not the supplementary product version.
"I trust myself to do my duty, even unto death. It's what comes after that I'm afraid of."
"Just fight without fear. Your soul is protected by the hand of Avacyn and will never submit to evil."