Best to redact using black rectangles. However, when you redact a PDF, make sure you don't just draw rectangles over the text, the text remains and can be easily extracted. Add the rectangle as is but then export to raster images like PNG/JPG then recombine these in a PDF.
If your redacted documents are to be printed, ensure that you first redact then print. If you must print then redact (let's say you prefer to redact a physical document), photocopy the redacted document and distribute that, so the text cannot be forensically recovered.
Anything else (blurs etc) are prone to reversal or leakage.
If your redacted documents are to be printed, ensure that you first redact then print. If you must print then redact (let's say you prefer to redact a physical document), photocopy the redacted document and distribute that, so the text cannot be forensically recovered.
Anything else (blurs etc) are prone to reversal or leakage.