MB3 192a: Cutting Paper (Including Toilet Paper) on Shabbos (340:13-14)

Ripping paper on Shabbos is considered תיקון כלי (and why it isn't classified as קורע).

Ripping toilet paper on Shabbos is a דאורייתא. If there's no ripped paper, one can rip with a שינוי because of כבוד הבריות.

Tearing paper to access what is inside (e.g. envelopes) vs. to use the paper (e.g. paper towels)

Gluing paper/hides together is a תולדה of sewing.