1. An image reading apparatus comprising: an image data acquiring unit configured to acquire document image data including more than one set of page image data; an image reading unit configured to read an image located at a predetermined page position from the acquired set of page image data; a conversion unit configured to recognize the read image of the predetermined page position and convert the recognized image into text data; and an order assigning unit configured to assign page number order to the set of page image data according to value information represented by the converted text data.