I have stuff marked w/ Sharpies that are 20 years old. They still look fine now. If you're really concerned, go to art store and they will direct you to pigmented ink pens. India ink is also definitely archival. Or mark it w/ acrylic paint and a little brush. It will last longer than the photograph. The pigmented stuff will sit on the surface and never bleed through. I don't think any of the other stuff will bleed either. It's more about proper storage.