I only use pdfs, but even in the tree-murdering days, I wrote, highlighted, and amended. I don't do that is literature, but an RPG book is a manual.
I remember having to initiial the coverletter on military manual updates to acknowledge that the unit copy had had the required pages replaced, or ocasionally, just deleted or inserted.
Yeah, the USAF and US Army occasionally delete whole pages of regulations, and if you're not the admin staff, you might not find out...
Post-it notes leave marks if left in for more than a few years. Early versions were particularly nasty, as they became acidic. Acid+Paper = brown. As in the black ink turns brown, and the paper turns brown. Knock off brands can leave damage after as little as a few weeks.
Oh, and as for laser printed? they can literally pull the toner off.
Work in an Achive for a couple years (I did - US NARA 12NS, Anchorage) and you learn quickly how damaging many convenience products are. The modern steel staple is one of the worst... it can corrode in as little as a year. The Galvanized staples the Army used for side-stapled field manuals, tho', that comes close to indestructible.
Brass staples don't corrode as fast (I've seen 120 year old documents with brass staples - not a wire staple, but a punched brass sheet oval with a spike at one end and hole in the opposite. I've seen these things look brand new and shiny despite the high-acid coarse-pulp paper they were used on going from ecru (presumably) to mil-chocolate in color. And the black iron ink turning to a barely perceptible redbrown.
Brass wire staples of the modern shape are also quite lasting. I've seen 100yo ones that had not discolored at all. I've seena few, however, that leached out copper oxide.
