1. A document management apparatus including one or more programs of instructions which are stored in a non-transitory storage medium and are executable by a processor of a host computer to configure the host computer to comprise: a comments extraction module to compare (a) a source document registered in a document repository and (b) a scan document image of the source document, to extract, from the document image, comments added to the source document and determine a position of the comments in the document image; a registration module to register the extracted comments and corresponding position, as comments content in association with the source document in the document repository; and a contents review module to provide, upon request, the comments content in a document review user interface.