Yeesh. This is above my pay grade. If I've got the same ID (or Pshop, or any other) file in a projects folder in Documents on both Macs, and I make changes to the file on Mac A, are you saying those changes will appear on the file on Mac B when I open it?. And if I make further changes to the file on Mac B, they'll appear on Mac A when I open it the next time?

I've got 55 gigs of iCloud space, so size shouldn't be an issue.