Blacking out a part of a PDF, or redaction of text

What methods are there to blackout a part of a PDF? I don't want to simply use Preview's annotation tools and then save the document, since then someone could open up the PDF and remove the annotation to reveal the part of the document which I'm trying to black out.

asked Aug 21, 2011 at 0:17 24.1k 84 84 gold badges 190 190 silver badges 291 291 bronze badges The correct term for what you want to do is "redaction". Commented Aug 21, 2011 at 1:17 Commented Aug 23, 2011 at 7:41

In macOS Big Sur, Preview.app has a built-in redact tool in the markup toolbar that takes permanent effect. Redacted contents are lost if the file is closed.

Commented Dec 9, 2020 at 10:26

12 Answers 12

If you want to leave it as a PDF, you really need to use the actual redaction tools in Adobe Acrobat, otherwise you are simply leaving yourself open to reversals.

If you want to save the PDF as a graphics file, then any black box over the words should work.

105 4 4 bronze badges answered Aug 21, 2011 at 2:45 lemonginger lemonginger 1,756 3 3 gold badges 16 16 silver badges 26 26 bronze badges

If you are looking for a no-cost way in Preview.app

  1. File->Export (or save as)
  2. Export PDF to TIFF file format (it's a multipage image format)
  3. Open TIFF file
  4. Export TIFF to PDF file format

Maintains page structure, OCR will be lost.

103k 42 42 gold badges 219 219 silver badges 270 270 bronze badges answered Sep 7, 2012 at 5:03 1,281 2 2 gold badges 8 8 silver badges 2 2 bronze badges This method was truly the best approach for me. No software installs necessary. Commented Sep 10, 2014 at 14:36

Would you care to comment how the feature of being able to go back to the previous version of a document comes into play here?

Commented Sep 20, 2014 at 0:29 @cnst: I think the idea is to create a redacted copy, and leave the original PDF alone. Commented Feb 17, 2015 at 17:38

Great solution. Note that in cases where using the TIFF document directly is acceptable, it's worth turning on compression for the TIFF export (e.g., LZW works on Windows, too), so as to prevent the file from becoming much larger than the original. (If you convert back to PDF, this is not necessary, because the conversion apparently applies compression implicitly).

Commented Feb 17, 2015 at 17:42 Try "Paintbrush" for OSX for a solid, free mspaint-like program to do the manual redacting. Commented Jan 28, 2016 at 22:35

A free solution, is to convert the PDF to an image, then save it as a PDF again. The only drawback is that the PDF will remove any OCR info it might have had.

  1. Open the PDF file to redact in Preview.
  2. Black out text using any method you want (e.g. use the rectangle annotation tool with black as the color and choose the thickest border. Then draw the shape as many times as needed until your document is blacked out.)
  3. File > Save As, and choose an image format such as PNG or GIF.
  4. Open the saved image file, then File > Save As, and choose PDF.
answered Sep 3, 2011 at 17:50 24.1k 84 84 gold badges 190 190 silver badges 291 291 bronze badges wow that's a painful brute force approach. Commented Feb 6, 2016 at 1:34

This is a better approach than the current leader, because it not only removes OCR, it blacks out stuff too.

Commented Nov 20, 2018 at 5:00 GIF is probably not the best option for this sort of thing Commented Mar 5, 2023 at 2:03

Big Sur’s Preview now has a Tools / Redact menu item that specifically deletes the content being redacted when the document is closed. More information in Apple’s Preview guide:

answered Jan 25, 2021 at 19:08 Robin Whittleton Robin Whittleton 301 1 1 gold badge 5 5 silver badges 21 21 bronze badges

PDFPen has a redaction tool which works properly.

answered Aug 21, 2011 at 13:53 Harald Hanche-Olsen Harald Hanche-Olsen 4,159 22 22 silver badges 22 22 bronze badges Beware though, of information in graphical, rather than textual form: This is harder to redact. Commented Aug 21, 2011 at 15:31 I believe that my original answer would work properly for graphical data. Commented Aug 23, 2011 at 6:47

@Senseful: No. I just tried it. The result is here. You can't tell by looking, but the file contains three images, layered atop each other: At the bottom the original images, and on top of that, the annotation rectangle and its border as two separate images. The pdfimages tool (comes with poppler, which I have via MacPorts) extracts all three images, letting me read the not-so-secret secret.

Commented Aug 23, 2011 at 20:19

Would saving the pdf as an image (eg GIF or PNG) in Preview, then saving that image as a PDF again properly redact graphical data? (ie, see apple.stackexchange.com/questions/22683/…) -- from my testing it seems to be a valid solution.

Commented Sep 3, 2011 at 17:51

@Senseful: Yes, that should work. However, in a multipage document, you would have to do that to every page, then reassemble the redacted pages afterwards. So it may not be the most practical solution, but I don't see any problems with it otherwise.

Commented Sep 6, 2011 at 19:42

OK, so the only real solution is to redact a paper copy and then scan it back in!

All other methods mentioned here don't work properly.

Importing the image in to GIMP and editing it there doesn't work, as once the page is put back in to a PDF document, that page is no longer text searchable as the whole page is now seen as an image!

Skim just doesn't work for redacting text. Or maybe it's just completely unintuitive with no good help.

Most other methods leave the text accessible beneath the redacted 'white outs'.

answered Sep 4, 2013 at 8:52 69 2 2 bronze badges

I opened the PDF in preview, exported it as a jpg. Opened word/pages and pasted the jpg into the document and then used a rectangle box to blackout whatever I wanted to and then I exported it as a pdf.

answered Mar 30, 2014 at 12:43 Karan Navani Karan Navani 29 1 1 bronze badge

ScanTango

Using a demo version today: the option to redact is greyed out, so I can't confirm its efficacy.

… the redaction tool worked pretty well. Actually, it even seemed to muck up the text in a live pdf document so you couldn’t copy what was under the redaction. … I can’t say how much I’d trust this feature with sensitive live text. I scanned all of my documents to PDF with no OCR before I did my redaction. Then, I printed to PDF to add one more layer of separation to make sure nobody could see what was behind the redactions.

answered Aug 23, 2011 at 9:04 Graham Perrin Graham Perrin 7,739 14 14 gold badges 82 82 silver badges 245 245 bronze badges

I tried saving my image as an image in preview and this only works if your pdf is one page. If it's multiple pages, exporting as an image will only save the first page.

The solution I found was this (it's a bit tedious, but you can get through it pretty fast once you get the hang of it):

Open PDF in GIMP (free photo editor) as an image. Only open those pages that need redaction. When you open it as an image, it essentially flattens the pdf so you're no longer able to highlight and copy text.

Use tools in GIMP to black out text.

Then, file -> print. On the print screen, choose "Print Preview". This will bring up the pdf in Preview where you can export/save the file.

If you have more than once page, then you can choose the thumbnail view in Preview and drag/drop the pdfs onto one another to form a larger document that you can then print. This is what I do when I have to sign just a few pages of a large pdf document.