1. An attaching method of attaching an additional image to a one-page image that is obtained by drawing one or more objects including at least one bitmap object in bitmap format in a predetermined sequence, the attaching method comprising: a) determining whether or not an object that is to be drawn is a bitmap object; b) if the object is determined to be a bitmap object in the step a), determining whether or not the object is a background object representing a background of the one-page image: and c) if the object is determined to be a background object in the step b), drawing an additional image after drawing the background object.