My three year old grandson wrote all over one of my prints. Don't press hard though, as you will remove the emulsion of the print. If a lot of pressure was used with the pencil, the print may have to be restored. If the writing is in pen, your options will depend upon the type of ink. Those have to be restored, as the damage is permanent.
T here are really two kinds of ink bases.
Water soluble and oil soluble. Water will not budge an oil soluble ink, and visa-versa. So if you are unsure, try the water first. For an oil based stain, I have often used something like paint thinner. I said paint thinner, not turpentine or acetone.