Just my opinion: Winner was either very naive or very ignorant to assume that any classified level document didn't have tracking IDs embedded into it. It's been a known thing for mole hunts for 70+ years... There's tons of declassified information that can be found in cold war era books on intelligence related matters about how false information is fed to known agents, and such.
nytimes:
"Ms. Winner, then 25, had been listening to the site’s podcast. She printed out a secret report on Russian cyberattacks on American voting software that seemed to address some of Mr. Greenwald’s doubts about Russian interference in the 2016 campaign and mailed it to The Intercept’s Washington, D.C., post office box in early May.
The Intercept scrambled to publish a story on the report, ignoring the most basic security precautions. The lead reporter on the story sent a copy of the document, which contained a crease showing it had been printed out, to the N.S.A. media affairs office, all but identifying Ms. Winner as the leaker."