Digital Watermark is a machine readable covert pattern in a digital image in either the digital or printed format. Often used to identify the copyright holder of a photograph.
This Digital Watermark feature is effective primarily in document-present situations where the original document can be examined by a trained professional or scanned with a specialized 3-illumination ID scanner and analyzed with adequate forgery detection technology.
Usability in online and mobile onboarding situations is challenging as the examination is made not on the physical document but on a photograph or scanned image of it.
Ref.: https://www.gpo.gov/pdfs/customers/security_glossary.pdf).
See also Fourdrinier Watermark