[Null]

i've done it before... i think what i did was open it up in image ready, then click the button that says edit in photoshop. which will have each layer as a different frame. take out the background in each layer leaving it transparent... clicking on edit in image ready, which would bring it back to image ready. then save the optimized file.

(not on my pc right now or i would try it out) but thats just off the top of my head remembering. only done it like once tho.