Document generation apparatus, a document producing method, a computer program and a recording medium

A document with a supplementary explanation in which a supplementary explanation character string is given in a ruby form in a character size which conforms to a character size of a document is easily, effectively generated. Information on a character size of a character in a character area is stored; the information on the character size is read to correct the information on the character size for each character area based on a character size of each character area; one character area is divided based on information on the corrected character size; information on a display form of a supplementary explanation character string is generated based on the information on the corrected character size when information on a character size is corrected for a character in a character area made by division; and a document with a supplementary explanation is generated based on the information on the display form.