An image processor is provided with an acquisition unit; a discriminating unit; a decomposing unit; and a rearranging unit. The acquisition unit acquires image data and layout information of an original document which are obtained by reading the original document in which the layout information is recorded in advance. The discriminating unit discriminates number of logical pages in the original document, an arranged order of the logical pages, and orientation of the original document, based on the layout information. The decomposing unit decomposes the image data into the logical pages, based on the result of the discriminating. The rearranging unit rearranges the decomposed logical pages according to a predetermined output layout, and outputs image data in which the logical pages has been rearranged.