To provide a control unit including a touch panel display capable of presenting preview display of multiple pages of document images on the display panel, the touch panel display includes: a binding position indicating controller; a binding process preview displaying controller that displays preview images of recording paper bound at the specified position; a paper binding position-linked scrolling display switching controller that, when the binding position in the printed paper is modified, switches the direction of scrolling preview display so as to be suited to the recording paper bound at the modified binding position.