A method is provided that enables verification of whether a component of original image data has been altered at the location at which the component is to be reused without newly generating a signature. More specifically, the method includes inputting first document data including a plurality of components and signature information corresponding to the components, selecting at least one component from among the components, and extracting signature information corresponding to the at least one selected component. The method further includes storing the at least one selected component and the signature information corresponding to the at least one selected component in a memory, and generating second document data by pasting the at least one stored component and the stored signature information into a document selected as a paste location.