Anyone know the status of steganographic tracking / watermarking for scanners? Like when you scan to PDF. There might be something plain-text/easy that ends up in the PDF file to identify the make/model/serial number of the scanner that might be straightforward to strip. But are there more subtle yellow-dot like things that might be harder to strip?

Also, almost all such watermarks would be easily destroyed by bitonalization and despeckling, which is usually done anyway to reduce the file size (e.g. it's part of the default operation of https://github.com/4lex4/scantailor-advanced ). Arguably the same is true for yellow dots if one is leaking scanned printouts, but identifying leakers is not the main purpose of the dots...

If one really wanted to, one could try embedding little holes into certain letters and hope they survive the smoothing algorithms and don't stand out too much. Not sure how successful that would be, though.