A document is divided into a plurality of regions so that each page has a meaning and, for each of the regions, there is generated a similarity table indicating a similarity degree and a data amount corresponding to the multiplexed resolution level data. By referencing this similarity table, each page of the electronic document in the region specified by the user is represented by a predetermined similarity (resolution) and at the reading speed specified by the user. Moreover, by referencing the similarity table, each page of the electronic document is represented at the maximum speed while guaranteeing the predetermined similarity.
