theyre microscopic. theyre typically used to track printers doing illegal stuff (e.g counterfeiting) and leak tracking if someone when to scan some document and post it somewhere it shouldnt be. Of course, this is antithetical to privacy. The yellow dots are microscopic throughout the page.

It's only common on color laser printers.

You can’t. They’re microscopic.

This isn’t entirely correct.

https://office-watch.com/2017/secret-printer-tracking-dots/

Generally they are not found in lower end budget inkjets, but are found in higher end ones.