Pens, pencils, and printers are not all alike. Others cause damage. Pencils are better than pens most of the time. Use a soft No. 2 pencil, writing lightly. Adhesives and such.
Staples are acceptable.
See what's wrong with tapes , strong , rubber bands , and paper clips , on the UIUC Library's preservation page. Don't force materials together Water damage. Put unfolded paper towels on each side of each wet sheet of paper. Browse or search the Harvard Library Preservation Database.