Printing from Photoshop for Mobile on an iPad is a very limited process. May I assume you are tapping the Share icon, then choosing "Publish and Export"? From there, you get to choose your format, and when you tap Export, that takes you to the iPad share menu, where you can send it to the printer with limited controls (dictated by iOS). Very unscientific and nothing to control the print size or quality.
Unfortunately, that is the state of things on the iPad so far. If you want more control over what you print, I recommend using Photoshop (or another capable application) on a desktop computer.