I spent years working in blank Intelligence areas and part of that time was teaching agents that the only safe way to redact was to put the black stuff in, print it, check it then scan the printouts back in as PDF's. You got a good electronic format, a searchable body and stuff that wasn't supposed to be there damn well wasn't.
I see not enough people listened.
Now that I am out of this stuff, I see it as a good thing that very unthinking people still do this stuff and don't even check it but it annoys the hell out of me professionally. .