Comment by limagnolia
8 hours ago
Are you saying that only Adobe PDF has proper redaction tools? I did a quick search and found several open source PDF tools claiming to do redaction- are they all faulty? I would honestly be surprised if there aren't any free tools that do it right.
No that's not what GP is saying. GP is saying that there is software that does not have a redaction feature (perhaps because the developer didn't implement it), but users of the software worked around it by adding a black rectangle to the PDF in such software, falsely believing it to be equivalent to redaction.
Properly implementing redaction is a complicated task. The redaction can be applied to text, so the software needs to find out which text is covered by the rectangle and remove it. The redaction can be applied to images, so the software needs to edit a dizzying array of image formats supported by PDF (including some formats frequently used by PDFs but used basically nowhere else, like JBIG2). The redaction can be applied to invisible text (such as OCR text of a scanned document). The redaction can be applied to vector shapes, so some moderately complicated geometry calculations are needed to break the vector shapes and partially delete them.
It's very easy to imagine having a basic PDF editor that does not have a redaction feature because implementing the feature is hard.
For the same reason, a basic PDF editor does not have a real crop feature. Such an editor adds a cropbox and keeps all the content outside the cropbox.