On Wednesday, 24 January 2018 23:14:10 UTC, ss wrote:
I have 3 `copies` of a document.
1 is original (ball point) and 2 are copies (laser printer)
They all look similar, so does anyone know of a way to differentiate the
`wet signature` from the copies.

Have a look for yellow dots using visible blue lights

https://en.wikipedia.org/wiki/Printer_steganography

http://seeingyellow.com/

Includes links to websites which can help you decode the dots

Owain