The surface of paper is not perfectly flat. It is actually a complex arrangement of individual paper fibers created during the manufacturing process. Using only a commodity desktop scanner and custom software, we measured the surface texture of a sheet of paper by scanning the document at multiple orientations.
On this document, we printed some text in Times New Roman 12pt font on normal copy paper. We then scanned the document several times and extracted the surface texture information. What we see is the 3D surface texture of the paper. The perceived embossing effect is actually the wax ink sitting on top of the paper surface. In the background, you can see the individual paper fibers, and variations in the paper surface.
The surface texture of each document is unique. We can use this natural 'watermark' to track documents and identify documents. This work has direct applications for counterfeit currency,art, and tickets, as well as serious implications for voting, most directly a degradation in the secrecy of paper ballots.