This clearly comes from the people who thought up my favourite piece of brain dead "security" from the TSA
When you enter the line to the security gate a TSA numpty checks your boarding pass to make sure you are allowed to join the line. Everyone joining the line has their boarding pass checked, this is a piece of paper often printed on a computer that says what flight you are on, its just about the easiest thing to fake in the history of fakery.
Then you lob everything into the x-ray machine, clearly needing to separate your laptop out as clearly its impossible to see stuff through that. Shoes of course, belts, internal organs...
Then as you step through the body scanner some TSA numpty says "boarding pass please". Pointing out that you've just put all your crap through the machine and that your boarding pass is with your passport and your wallet is of course pointless. The answer... wait until it comes out of the machine and then show the numpty. you are of course also checked at the gate with both passport (hard to fake) and boarding pass (trivial to fake).
So in otherwords the TSA check TWICE a piece of easy to fake information and NEVER check your ruddy passport.
So how did the TSA redact this PDF. Well simple they had the same process. The first person pasted on the black squares. This was then printed out.
The first checker then looked at the printed out copy and said "looks fine to me"
This document was then scanned in and then printed again to be checked by a second checker who said "yup all okay"
And then they put the ORIGINIAL electronic copy on line with the pasting over the top.
The TSA is to security what Micheal Vick is to Pet Care