That said, after 15 minutes of gently massaging the PDF with claude, it was pretty easy to drop the substitutions and restore the original text.
So I built "SoulsOnly.ttf": a font for humans not AI, and keyboard firmware to type in it.
The implementation of a font can be "hacked" to make what looks like gobbledegook to a computer, render as legible to humans. Copying and pasting text written in the font into AI to summarize is almost impossible. And to avoid AI image analysis, a version of the font can be loaded with the glyphs scattered and require a simple "focus" interaction by the reader to begin reading. Note that a sufficiently prompted AI agent can definitely read this, so it's not meant to be cryptographically sound, more just unfriendly to the common AI reader!