An apparatus for and a method of image forming which embeds digital watermark information into an image data of a document and outputs the image data that includes determining the page of the document in which the digital watermark information is to be embedded based on a predetermined condition, the predetermined condition corresponding to whether the document is composed of two or more pages, embedding the digital watermark information into the page of the document determined by the above described determination and outputting the image data which is embedded in the digital watermark information by the above described embedding.