Those Sneaky Dots
As I have been pointing out in the GroundRod courses for years, your printer can "tattle" on you.
Case in point:
"According to Rob Graham, who writes for the blog Errata Security, the Intercept’s scanned images of the intelligence report contained tracking dots — small, barely visible yellow dots that show “exactly when and where documents, any document, is printed.” Nearly all modern color printers feature such tracking markers, which are used to identify a printer’s serial number and the date and time a page was printed."
So the most recent NSA leaker was rather quickly outed due to barely visible yellow dots that are surreptitiously placed into every document printed by nearly every printer in existence.
I encourage you to check out the EFF's guide HERE for finding and decoding your printer's secret messages.