1. An image processing apparatus capable of managing a document, said image processing apparatus comprising: a memory for storing an instruction; and a processor for executing said instruction, said processor being configured to generate a first additional image based on an image in a designated region of said document, generate a second additional image showing a difference between said document and a document before revision of said document, and register said first additional image and said second additional image on another device in association with a marker image showing a revision stage of said document.