But there is something to the idea that paper is a uniquely painful weapon.
To the naked eye, it might seem as if a paper’s edge is fairly straight and smooth. But if you were to zoom in, you’d find that paper is more akin to a saw than to a blade. So when a paper cuts open your skin, it leaves behind a chaotic path of destruction rather than a smooth laceration. It rips, tears, and shreds your skin, rather than making clean slice, as a razor or knife blade would do. (Source)