1. An image forming apparatus comprising: a read unit reading an image of a source document and obtaining image data; an electronic document production unit producing electronic document data for allowing a display apparatus to display said image data thereon, based on said image data; an extraction unit extracting from said image data an additionally-written region including an additionally-handwritten portion; a production unit producing annotation data based on said additionally-written region; and a setting unit calculating a position for allowing said display apparatus to display said annotation data on said electronic document data, based on a position of said additionally-written region on said image data, and setting the calculated position for said annotation data.