1. An image processing apparatus comprising: a character recognition unit configured to execute character recognition processing for a plurality of character images in a document image to obtain character codes corresponding to the respective character images; and a generation unit configured to generate a digital document, wherein the digital document includes the document image, a plurality of character codes obtained by said character recognition unit, glyph data, and a description required to render the glyph data corresponding to the plurality of character codes with a size smaller than sizes of the character images at positions corresponding to the character images in the document image, wherein the glyph data is used commonly to the plurality of character codes when rendering characters corresponding to the plurality of character codes, and wherein a shape indicated by the glyph data does not depend on character shapes of the plurality of character images.