When plotted against a grid, these yellow dots denoted specific hours, minutes, dates and numbers. Thus by reverse-engineering the grid pattern, researchers were able to discover the document had ...

The dots also encode a serial number for the printer. These “microdots” are well known to security researchers and civil liberties campaigners. Many colour printers add them to documents ...

put the "serial number of each machine coded in little yellow dots" in every printout. The millimeter-sized dots appear about every inch on a page, nestled within the printed words and margins.