I regularly print nine 5x7 cards at a time (7x10 before folding) on 24 inch wide rolls of Epson Premium Matte. I then use a 36 inch Rototrim cutter to cut the cards a bit oversized, by 1/8- 1/4 inch on a side. This part goes very quickly. I use the front edge of my Rototrim ( the long side opposite the rotary trimming wheel) to carefully line up and initiate the fold, creasing the paper to approximately a right angle by sliding my thumb across the paper at the point of the fold. Next, a bone burnisher shaped like a dull butter-knife is used to finish the crease. I then do the final trimming of the card to the final size. This is an important step: don't do the final trim until the fold has been made. If your fold is just a touch off, you can still save the card with judicious final trimming. Once you have done a few it goes fairly quickly, but 100 cards will definately take a couple of hours with my method. There may be better ways, but I have done hundreds of cards this way with good success.