Photoshop 4 but then a lot of newer software can. You have to marquee an area for editing, use the pick tool for a single colour or the rubber stamp to crib an adjacent area and dab it in the scratch or smudge. It does take time but just changing a white scratch to a black one can reap dividends. The magic wand tool can pick an area of single colour (adjust for tolerance to intensity) but to cover the scratch "enlarging" the area helps. Enlarging the whole picture often impresses people.
I did one for Joy's mother that had a biro "X" to identify a person. I took out the blue, only to find mom had put it back in to identify the person. She didn't understand that if I could remove blue I could have done an oval marquee (selection area) and upped the brightness to halo the person !