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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.

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The correct term for what you want to do is "redaction". –  Wheat Williams Aug 21 '11 at 1:17
A broader question in Super User (not limited to Apple): How can I obscure the text in a PDF file (e.g. "greek" it, or replace the text with Lorem Ipsum) –  Graham Perrin Aug 23 '11 at 7:41

10 Answers 10

up vote 5 down vote accepted

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.

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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.

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This method was truly the best approach for me. No software installs necessary. –  Sonny Sep 10 '14 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? –  cnst Sep 20 '14 at 0:29
@cnst: I think the idea is to create a redacted copy, and leave the original PDF alone. –  mklement0 Feb 17 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). –  mklement0 Feb 17 at 17:42

PDFPen has a redaction tool which works properly.

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Beware though, of information in graphical, rather than textual form: This is harder to redact. –  Harald Hanche-Olsen Aug 21 '11 at 15:31
I believe that my original answer would work properly for graphical data. –  Senseful Aug 23 '11 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. –  Harald Hanche-Olsen Aug 23 '11 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. –  Senseful Sep 3 '11 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. –  Harald Hanche-Olsen Sep 6 '11 at 19:42

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.
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Open your PDF or image.

Use the line tool or whatever to make your redactions.

Then File>Print. Instead of printing to paper, save it as a PDF. Doing it this way causes the black lines or boxes to no longer be clickable. If you just "save as" a new PDF, the boxes remain able to be manipulated,

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Sadly, this approach has one fatal flaw: if you redacted by simply placing opaque boxes over the content of interest, you can still select and copy & paste the obscured content; also, hyperlinks in the obscured content continue to work, too. –  mklement0 Feb 17 at 17:02

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.

Hope this helps!

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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'.

I have given feedback to Apple about this (http://www.apple.com/feedback/macosx.html)

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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.

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Features include redaction.

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

According to a 2008 post by Adam Greivell:

… 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.

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PDF Studio version 8 has a manual redaction tool built-in its content editing tool. It is real redaction that actually removes content. It can select text and images in the PDF document content and redact them.

PDF Studio version 9 (coming March 2014) will have a full fledged redaction feature where users can select an area on a document, and it will redact any images or text intersecting with this area.

PDF Studio works on Mac (including 10.9 Mavericks) but also Windows and Linux and the same license key can be used on 2 different computers with different OS.


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