Stains happen, even if you think you're being careful when using a pen while seated on your favorite leather furniture. Instead of reaching for harsh chemicals that may damage the upholstery, remove those ink spots with safer household options such as toothpaste or rubbing alcohol. The same solutions can be used to remove ink stains on vinyl and faux-leather furniture as well. Test any stain treatment in an inconspicuous area first to ensure it does not discolor the leather.
Ink stains that are fresh are far easier to remove than those that have set for days, or longer. As soon as you notice that stain, rub it with an art-gum eraser or white eraser. Check the eraser frequently and clean it off by rubbing the inked area onto a sheet of paper before continuing on the leather stain. Rub the eraser mostly in the same direction as the ink line, rather than across it, to avoid damaging the leather finish or spreading the ink.
Rubbing alcohol takes ink off of many types of materials, including leather. To remove a few small scribbles, dip a cotton swab in rubbing alcohol; then wipe the ink marks,, following the lines from one end to the other. Replace the swab with a fresh alcohol-dipped swab once the first swab becomes dirty. Avoid rubbing across the ink lines, as this may cause the ink to "bleed" and spread. For larger stains such as ink blobs from a broken pen, dip a cotton ball or soft white cloth in alcohol; then dab the stain, rotating the cloth or cotton frequently to avoid spreading the ink.
Dab a small amount of a non-gel white or light-colored toothpaste on your finger; then apply it to the ink stain. After several minutes, wipe the area with a clean damp sponge; blot the leather dry with a soft cloth. Do not soak the leather as you remove the toothpaste, as the leather may absorb the water.
Ink on leather is such as common problem that there's even a dedicated product designed specifically for treating such stains. Rub an ink-removal stick -- the type made for leather and sold in leather-goods shops -- over the ink stain, wiping the ink off the stick with a paper towel as the ink transfers over. If the stain is not fresh, rub the ink-remover stick over the stain; then scrub the spot gently with a wet toothbrush until the solution foams. Blot the area with a white cloth, and apply a leather conditioner over the treated area to keep the leather soft and supple.