pdf files

Is there a way to alter the way pdf files are displayed? As in change the text color or background color?

the prop. adobe reader has this hidden feature under "accessibility"..
(which borders on discrimination but i dont want to go down that road…)
as far as other readers go, i have found none yet.. would appreciate to hear from them! I like it much more to read white text on a darkgray background than black on white...