[jareklupinski]

you have to compare (at least) two independently sourced copies of any document to make sure it hasn't been adulterated by third-parties in-transit

attribution doesn't even have to be hidden: if it's easy enough for someone to stamp unique watermarks for every person's copy of their pdfs, it's just as easy to ++/--/randomize any field, which can just as easily reveal the source (only employee xyz had value 123.010 in field abc, everyone else had 123.01 or 0123.01)