1. An image forming apparatus being able to print a manuscript to an index paper, wherein the manuscript comprises text and wherein the index paper comprises a standard size section and an index label section, the image forming apparatus comprising: a display part, wherein the display part displays an index label setting screen that includes: a box for displaying and receiving user input of index label text printed in an index label, and a check box for receiving a user input to: set the text of the manuscript to print to the standard size section and the index label section, and thereby cause the display part to display a shift image indicating the text which is printed to both the standard size section and the index label section, and wherein the standard size section includes an A4 size section or a letter size section, wherein the index label section is provided outside of the standard size section; an index label information setting part that sets up index label information via the index label setting screen; an index label preview display part that displays, in the index label setting screen, a first preview including the index label that is set by the index label information; a shift size setting part that sets up a value of a shift size for moving the text of the manuscript; an image area shifting part that moves the text of the manuscript only the value of the shift size; and a shift image display part that displays, in the index label setting screen, a second preview including a preview of the index label, wherein, if the text which is printed to the standard size section and the index label section is set to the manuscript text by the check box being checked, the second preview is displayed, wherein the second preview displays a preview of the setting result of the shift size value for moving the text in the manuscript by expressing the manuscript text as a belt pattern, and wherein, when the check box is checked, even if the index label text printed in the index label is set to the box in the index label setting screen, the index label text is not displayed on the index label included in the second preview.