Department of Homeland security placed nearly invisible watermarks on all real ballots. Only a few highly placed officials knew of this security measure.
Millions of mailed in ballots that are being counted do not have the water mark.

Problem with this stupid theory is that each county in each state prints their own ballots.
Did President Trump issue secret watermarks on ballots? No, that’s another QAnon conspiracy theory
This is a bogus conspiracy theory.
The federal government has no role in printing ballots or in the on-the-ground mechanics of elections. The responsibility lies with state and local governments.
Some states may require a watermark on ballots, but there is no evidence of a secret Trump-issued watermark on “official ballots.”