I imagine it would very difficult to read these dots from a distance and dynamically. I just mention it because most printed documents already have indentifiers printed on them that don't require seeing individual fibers.
Fun fact: Otavio Good, who led the winning team, learned about the printer dots on this very site. As I recall, he said that the dots were like a map that let them reconstruct the shredded documents.
I would had thought, even then, that this was not only commonly known, but not the sole only annulment/rule among a generally "rules-free" competition, having been rather obvious, especially to the audience these competitions attract.
Thank you for reminding me, and others, how immediate and obvious success can be.
I'm not sure if there's a source online as I learned about it from Otavio directly. The slightly longer story, as I recall it, is that their team basically built a "game" to help humans unshred documents, and was using that approach until Otavio happened to read about the printer dots on HN. He updated his code to take those into account and was astonished at how helpful they were.
