"I would just" [do this slightly more complicated transformation] really misses the point. Nobody disputes the fact that you could turn any given human-readable pdf into an untraceable version. E.g. you could copy it all out longhand and make sketches of all the plots. Certainly it would work. The point is that as the necessary transformation becomes more complicated/more work, the fraction of the population that will actually do it will vanish, and the surveillance scheme will be effective again.