Yes, XEROX is a Scrabble word!

Letter values in Scrabble US: X 8, E 1, R 1, O 1, X 8.

Is it a valid word?

XEROX is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a copy made by a xerographic printer
a duplicator (trade mark Xerox) that copies graphic matter by the action of light on an electrically charged photoconductive insulating surface in which the latent image is developed with a resinous powder

Also: xerox copy, xerographic copier, xerox machine, run off.