When you have printed your layout it is a simple matter to turn the page over and put some information on the back, such as when and where the photos were taken and the dates. Name the subjects in the photos, and add your name as the layout maker. You can add as much information as you want. After being the recipient of some photos well over 100 years old, I can tell you how glad I'd be to have that kind of information! Pencil markings fade and rub off, pens are a no-no because of acid or pressure which can dent the paper, so printing is an ideal solution. You already have your size set up, so it is easy to just add text with your graphics program. I usually use a medium gray color that won't ever show through. A hundred years from now they'll still be thanking you!