Disclosed is an information processing system having a print preview function for displaying a preview of the printed state of a document before the document is printed. If a double-sided printing function has been set by a user interface for setting various print functions for a document, a preview of front and back pages is displayed with the spacing between the front and back pages narrowed or the display positions thereof made different from each other in such a manner that pairs of front and back pages may be recognized at a glance.
A method of indicating a paper insertion direction, the method including displaying an image of a paper cassette when a user tries to insert a paper on which other contents are previously printed into the paper cassette to print predetermined contents; displaying an expected print result indicating whether a to-be-printed side is on the same as a preprinted side of the paper and whether the to-be-printed side has the same up/down direction as the preprinted side; and displaying images that distinguish between front and rear sides of the paper and between up and down directions with respect to the preprinted side based on the expected print result. Also, a method of indicating a preprinted paper insertion direction and alarming improper insertion when inserting a preprinted paper into a printer, the method including displaying the preprinted paper insertion direction into a paper cassette on a display unit in the printer; determining whether the preprinted paper is properly inserted into the paper cassette; and outputting an alarm message if the preprinted paper is not properly inserted into the paper cassette.
