I just spent the better part of the day on a design for business cards, only to find out now that I was working with the wrong file format. Basically, I end up with my PS document with layers (RGB) and now I need it in CMYK at 300dpi. Can I just save as is, then open a new document at 300dpi, in cmyk, then pull my project onto the new (correct) format document, and resave? It can't be as easy as that can it? Probably not.