Re: Very strange
The documents were in readable format and not encrypted so that they could be tracked, every document that gets printed in this environment has unique but very minor changes that are recorded and allow anyone seeing the "revealed" printed document to know who did it.
For example, the original document could say "This is an important document" but the printed version might say "This is a important document" ... a minor change or two in a printed version that allows each unique printed version to be identified but most readers would just read straight past it.