1. A method for controlling an image forming apparatus, comprising: reading an original image to which a copy-forgery-inhibited pattern and copy restriction information for restricting a number of times of copying are added, the copy-forgery-inhibited pattern including a latent-image part and background-image part, when the copy-forgery-inhibited pattern is copied, the latent-image part in the copy-forgery-inhibited pattern appears in the copied image; determining the copy restriction information read from the original image; removing the copy-forgery-inhibited pattern from the original image; updating the copy restriction information; and forming, on a sheet, the copy restriction information with the image from which the copy-forgery-inhibited pattern has been removed from the original image.