How To Redact a PDF: The Proven Best Method

Search for “How to redact a PDF” and you’ll get multiple answers. But do all popular methods of redaction work? We’ve put them to the test to find out. 

Redaction. The word has been around for hundreds of years, but it’s only recently entered our vocabulary as meaning “content removal.” The new definition came out of national security and legal usage, which is probably why most of us associate it with secrecy. In 2019, redaction got its 15 minutes of fame when lawyers in a high-profile case attempted to redact passages in a court filing and failed. Since then, it has continued to make news, recently as a point of contention in Ghislaine Maxwell’s case and as a reason for UFO enthusiasts to speculate.

Around (at least) since World War II, when the US Military Postal Service allegedly redacted soldiers’ letters, redaction has been attempted in multiple ways. We’ve narrowed the list of methods down to four, and pitted them head-to-head in a competition of efficiency and risk mitigation. Efficiency deals with how simple and quick the method is; risk mitigation is about how effective it is in removing sensitive content. 

Inspired by myicedtea

1. Color over the sensitive content with a Black Sharpie.
2. Scan the document.

There’s something pleasantly nostalgic about getting a Sharpie out and using it to black out pseudo-classified information—in this case, the name José "Pepito" Gómez, which, in fairness, should be more well-known. 

But if you look hard enough at the resulting scan, you’ll see that it’s actually possible to make out his name, even though we used a Sharpie on it twice.

This proves that the Sharpie method is, sadly, ineffective. And though we didn’t test it, we know it isn’t efficient, either. Yes, it was easy, and somewhat pleasant, to black out José "Pepito" Gómez on a page once (twice, actually, since we did a double layer with the Sharpie)—but what if the name repeated itself throughout a lengthy document? It would not have been easy to find and redact 37 occurrences of José "Pepito" Gómez scattered across 200 pages. Nor pleasant. Worst of all, it wouldn’t have worked. 

Inspired by Extract Systems

1. Use scissors to cut out the sensitive content.
2. Use opaque tape to cover the gap.
3. Scan the document. 

Literally cutting out a name from a document and then covering it up with tape is an interesting experiment with effective (although perhaps not aesthetically pleasing) results. We had never done it before and will never do it again, unless unforeseen circumstances force us to. We consider this method to be impractical, difficult (especially when you’re dealing with minimal line spacing), and slightly barbaric—it requires the use of a white arm, after all. 

Inspired by Serel Jadzia

1. Take a screenshot of the document.
2. Open the screenshot in Preview.
3. Place a black rectangle over the sensitive content. 
4. Convert the image to PDF.

Serel’s method actually works. We did what he instructed in this Quora thread and it passed the PDFpen optical character recognition test, meaning: we were not able to remove the black box and read what was underneath. Impressive! We could definitely recommend this method for redacting a small number of things on a small number of pages—it isn’t super time-consuming and there’s no risk of exposure, which is great. That said, it isn’t a viable option for redacting lengthy documents.

Inspired by our product

1. Open the document in PDFpen and select the sensitive content.
2. Choose Format > Redact Text - Block or Format > Redact Text - Erase.

OK, you knew this was coming. PDFpen’s Redact Text is to the cut-out method what email is to the smoke signal. It’s simple. It’s fast. It’s 100% guaranteed. When it comes to how to redact a PDF, we knew PDFpen would be the most efficient method, and yet we were still compelled to test it—because it’s such a neat, easy-to-use tool. 

The best thing about PDFpen redaction, though, is the “find and redact” feature, which enables you to remove ALL occurrences of a name, code, or phrase from a lengthy document in seconds.

Imagine quickly fulfilling your duty to protect privacy and confidentiality in a way that’s guaranteed to work. It’s the kind of thing that helps you sleep well at night. 

Not sure how to redact a PDF? There are various known methods of redaction:

• The Sharpie method is a fallacy. It does not work. myicedtea was right when they said, “I can still read what’s underneath and so can everyone else.” 
• We cannot think of a reason why you would want to use the cut-out method, unless perhaps you enjoy being crafty and have a ridiculous amount of time? In which case, go ahead—it works. 
• For a simple, elegant, and free way to redact information on a small number of pages, try the screenshot method. It works, and is efficient enough if you’re working with just a couple of pages. 
• If you’re dealing with sensitive or confidential information—court filings, national security agency manuals—do yourself and your clients a favor: use a redaction tool. 

PDFpen’s redaction tool guarantees text removal. Download a 30-day free trial.