This topic is not totally new to me. I think 2 or 3 years ago I found this list from the EFF (Electronic Frontier Foundation) but then I lost the topic. I recovered it while reading about printed documents being used in a lawsuit as a demonstration on origin finding with imprinted tracking dots, more common know as watermarks. The EFF still features this list of printers which do or do not imprint those tracking stuff.
So if you need to print some really private documents you should get your hands on one of those printers first.
http://www.eff.org/pages/list-printers-which-do-or-do-not-display-tracking-dots
Some models are available at eBay for a fair deal.