A segment extracting section extracts, from a document image, a segment that is an image region containing a series of text characters of a uniform size from a document image. When the segment extracting section extracts a plurality of segments, a segment designating section designates one or more of the extracted segments each as an enlargement segment according to text sizes of the respective extracted segments. A scaling-factor determining section determines a scaling factor for each enlargement segment based on the text size of the enlargement segment and a standard text size. An image creating section enlarges each enlargement segment at the scaling factor determined for the enlargement segment and creates a page image including each enlargement segment as enlarged and each non-enlargement segment that is an undesignated segment among the extracted segments.