I have a PDF for my camera's manual, and Adobe Reader won't let me print it (the print option is grayed out). SumatraPDF also does the same thing (it even says print denied). How does the PDF prevent itself from being printed? It seems that if the program can display it on the screen, then it can also print it. Maybe Adobe Reader respects the PDF not printing, but surely an open source PDF reader wouldn't be so restrictive. So is there something more to this than merely the PDF reader software respecting the PDF's request to not be able to be printed?