Wasn’t there a patent, at least ten years ago, for something very very similar?
A random sprinkling of aluminum fibers (invisible t the naked eye), mixed in paper pulp, creating an electronically discernible ‘finger print’ for any piece/page of paper,logged and tracked and track-able even after years of natural wear-n-tear? There is no practicable upper limit to the number of uniquely identifiable pieces of paper using this simple method.
The principal described in the posted patient is not a stretch to achieve, with only the random distribution of injected ‘reflective’ dust.