Photostatting is a technique of making copies of documents or images using a photocopier or photostat machine. Synonyms for photostatting could include photocopying, duplicating, reproducing, replicating, copying, cloning, mirroring, or mirroring-reflecting. Each of these words could have slightly different connotations, such as duplicating indicating an exact copy, while replicating could imply a bit more flexibility or variation in the final product. Cloning might be used more for science experiments than for document copying. But all of these words would be good choices to communicate the idea of creating a copy of an original document or image.