A list of a plurality of objects to be displayed, which corresponds to page images to be operated, respectively, is displayed; it is determined which object is selected as an object to be moved among the plurality of displayed objects to be displayed; it is determined which object is selected as a movement destination object among the plurality of displayed objects to be displayed; and allocation page images are displayed in a state where a page image corresponding to the object determined as the object to be moved and a page image corresponding to the object determined as the movement destination object are allocated to a single page.