and not by just drawing that box over them in the original (textual content) pdf. You need to squash it down to images, then destroy the bits you need to. (Ther

and not by just drawing that box over them in the original (textual content) pdf. You need to squash it down to images, then destroy the bits you need to. (There might be other ways, but enough Big Government Agencies have screwed it up to make it worth noting) Is the 'decoding' paper this one: http://dheera.net/projects/blur.php http://dheera.net/projects/blur.php ? The blur function is just smearing pixel values across their neighbours in blocks, so you can treat it as a hashing function, and then generate enough candidates that eventually you get something that hashes correct (or close enough) I'm not sure how practical it'd be on data longer than a credit-card number, but it's an interesting hack nevertheless.