The EFF have been vocal about this for a while … it’s the worst kept secret that still few know about, and worth spreading!
Of course it can be obfuscated - but you need to know how to specifically upset the code:
Timo Richter, Stephan Escher, Dagmar Schönfeld, and Thorsten Strufe reckon they’ve cracked the challenge of knowing how to anonymise printed documents, and presented their work to the Association of Computer Machinery’s 6th ACM Workshop on Information Hiding and Multimedia Security in Innsbruck, Austria last week.
In this paper, the TU Dresden researchers explain that they tested 1,286 documents printed on machines from 18 manufacturers, creating an extraction algorithm to identify well-known dot-patterns – and at the same time, discovering four previously undiscovered patterns coding at 48, 64, 69, and 98 bits.
It’s amusing, and not, that this all goes on right in front of our eyes … and doesn’t …
… a little like the Eurion constellation, which has been around for over 20 years, which is more about devices that rebel against your command than leaking information, though I did read somewhere that it was thought scanners that detected the constellation sent messages to ‘concerned parties’ …
… no need to be alarmed … 
