1. A document display device comprising: a generator that generates a plurality of page images of a print job, each of the plurality of page images being an image of a double-page spread of a saddle-stitched document being laid out on an image of a recording medium; and a display that displays the plurality of page images, wherein the display displays the plurality of page images so that one page image of the plurality of page images is changed to represent a state in which at least a part of the one page image is turned and thus at least a part of another page image hidden behind the one page image is shown, wherein the display visibly displays an image of a part of staples placed at a substantially center part of the image of the recording medium when any pages are opened and the image of the recoding medium is turned around a position of the saddle-stitching, the pages being turned at the substantially center part of the image of the recording medium, and wherein, after the plurality of page images are physically printed out as the saddle-stitched document, a physical part of the staples corresponding to the image of the part of the staples is visible when a first page, a center page, or a last page of the saddle-stitched document is visible.