Hello,
sorry for the late response, it seems that this threat fell into my
"answered" folder without having been answered at all :/
First of all, it seems that you're good at making useful tools Micah ;)
One of the biggest challenges for MAT was (is?) to have a clean and
usable interface; I honestly don't want to design one to allow users to
add black stripes on PDF on my own; although I'll be super-happy to
review'n'merge such features of course.
My re-rendering method to sanitize PDF has the benefit of not destroying
the semantic of the document, the text is still selectable, so are
images, … this is not the case when putting everything into a PNG, but
on the other hand, cairo is a big pile of code, and processing PDF is
tricky, so it's likely that your method may be safer.
I don't think that it would be realistic to try to merge our two tools,
but I think it's worth advertising each one as a complement to the other.
Cheers,