Even though my computer says 100%, my printer has a mind of its own. Print out then measure. If the inch is off, I adjust the size on the printer. I usually make several copies after the size is exact. I keep one for a master.
Also I have printed on Pellon quilter's grid attached to a 8.5 x 11 sheet of label stock. You can leave the Pellon attached to your square. This stabilizes your work and prevents paper pieced squares from "growing".