We did it several years ago, but my recollection is that they took a bunch of photos at the photo shoot, and put all of them on our Photopass card. They also gave us a coupon for 1 free print.
I'm not sure if the coupon had an expiration date, because we used it immediately. We went right into the photo place. They took our Photopass card and showed us all of the pictures on it. They then let us choose which one to use for the free print. We could have used any of them, but I hear they have since restricted you to getting the free print from the photo shoot photos.
I know we saw all of our Photopass photos because we got to see a "magic shot" without the magic. In the photo, we were sitting on a bench looking shocked and pointing at nothing. The Stitch character hadn't been digitally added yet. The pre-magic picture was hysterical. I wish we had thought to get a print of that one.