Make sure the stain is fresh, as it will be much easier to remove. Place a piece of paper towel behind the stained paper to protect the surface beneath. Do this especially if it is a page in a book, since you don't want chemicals going through other pages.
Dilute oxalic acid with water. Dab the solution onto the permanent marker ink with a cotton swab, cotton ball, or paper towel. Continue to moisten the spot with drops of water, drying each time with a paper towel or blotting paper until the stain disappears. Use a clean cloth to remove excess oxalic solution.
Put the stained sheet in between two clean white blotting papers. Set aside for a few days to dry.