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How to Black Out Text in a PDF

To black out text in a PDF, use a redaction tool, not a black shape. A black rectangle only covers the text, so the text stays in the file and someone can copy it. A redaction tool removes the text and leaves a black bar. After you redact the file, read each page and test the file before you share it.

This article gives steps for three tools: our free PDF Redactor, Adobe Acrobat and Preview on macOS. It also gives the results of a real test with a made-up PDF, and steps to test your own file. For the general meaning of the word, read what redacted means.

Why does a black rectangle not remove text?

A PDF page is a list of drawing commands. A black rectangle is one more command. It does not delete the commands that draw the text. These lines are from the test file in this article. The first line draws the private text. The last two lines draw a black rectangle on top of it:

BT 1 0 0 1 60 585.8898 Tm /F1 11 Tf 13.2 TL (Morgan Sample, morgan.sample@example.com, client code BLUE-HERON-4471) Tj ET
BT 1 0 0 1 60 549.8898 Tm /F1 11 Tf 13.2 TL (This line is not private.) Tj ET
0 0 0 rg
n 58 582.8898 402.123 14 re f*

The screen shows a black bar, but the text is still in the file. A tool that reads the text does not stop at the rectangle.

A shape can also stay editable. Apple's Preview guide says that File > Save will "allow annotations to be edited later." It also says that File > Print, then Save as PDF, will "flatten annotations (so that they can't be edited)." The page does not say that flattening removes text under a shape, and we did not test this. Use a redaction tool.

How to black out text with the PDF Redactor

The PDF Redactor is free and runs in your browser. Your file stays on your device or secure network and never touches our servers. The tool does not edit the old file. It makes a new PDF from images of the pages, with the bars drawn in. We ran these steps in the test below.

  1. Choose a PDF or drop it on the page.
  2. Turn on AI if your PDF has names. The AI finds names, organizations and places. For English, the model is 29 MB. With AI off, the tool finds items such as emails, phone numbers, cards and ID numbers.
  3. Choose what to hide with the category buttons. Some items have bars at the start. In our test, the date had a bar. If a reader needs the dates, click Dates & ages to show them.
  4. Add your own words. Type them in Always hide these words, with a comma between them.
  5. Read each page. The tool does not find everything. Click a bar to show the text under it. Drag on a page to add a bar.
  6. Click Download redacted PDF. Keep your original file if you need it, because you cannot undo the redaction after you download.

Each page of the new PDF is an image. You cannot select, copy or search its text, and links, bookmarks and form fields are not kept. You can read what the page loads in our privacy policy.

How to black out text in Adobe Acrobat

Adobe says that this tool is "Available only in Acrobat Pro, Premium, or Studio." We took these steps from Adobe pages that we read on November 4, 2026. We did not run them, because we did not test Acrobat.

  1. Open the tool. Open a file, select All tools, then choose Redact a PDF.
  2. Mark the text. Select Redact text and images, then use the cursor to select the content.
  3. Find repeated text, if you need to. Select Find text and redact, then search for a word, a phrase or a pattern. In the results, check the boxes and select Mark checked results for redaction.
  4. Apply the marks. Select Apply in the Redact a PDF panel.
  5. Remove hidden information. Select Continue to sanitize and remove hidden information. Adobe says that after you confirm, "the redactions and hidden information are permanently removed and saved to a new file."

A mark alone does not remove text. Adobe's how-to page says, "The items aren't permanently removed from the document until you save it." That page also uses a different menu path, "Select Tools, then Redact", so your menu names can be different. Open the new file, read each page, and test it as shown below.

How to black out text in Preview on macOS

We took these steps from Apple's Preview guide, which we read on November 4, 2026. We did not run them, because we did not test Preview.

  1. Make a copy of the PDF. Apple's guide for macOS Sonoma 14 says, "To safeguard the original document, create a duplicate to redact."
  2. Open the copy. Go to the Preview app on your Mac and open the PDF.
  3. Show the tools. Click the Show Markup Toolbar button, if the Markup toolbar is not showing.
  4. Mark the text. Use the Redaction Selection tool in the toolbar and select the text. The guide for macOS Big Sur 11 calls this tool Redact Selection.
  5. Close the file. Apple says that "once you close the document, the redaction becomes permanent." You can change the redaction before you close the document.

Read these limits on Apple's page:

Because of this, test the closed file as shown below, and read each page.

Our test: a made-up PDF with a black rectangle

How we tested. On November 4, 2026, we used a script with the ReportLab library to make a one-page letter. All names and numbers in it are made up. A black rectangle covers one line: "Morgan Sample, morgan.sample@example.com, client code BLUE-HERON-4471". The other lines are visible. We opened the file in the actual tools, in Chrome, from a local build of this site. We also read the files with the command-line tools pdftotext, pdfinfo and pdfimages.

What the Redaction Checker found in the black rectangle file

The Redaction Checker showed "1 page checked · 1 leak found. See the list below." The finding was:

[LEAK] Text under black bars
These words are covered on the page, but anyone can copy them from the file.
  - Page 1: Morgan Sample, morgan.sample@example.com, client code BLUE-HERON-4471

It also listed the made-up title and author in the metadata as points to check. The command pdftotext printed the covered line too, so we did not need our own tool to read it.

What the PDF Redactor did with the same file

  • Bars with AI off: 5 bars, on the visible email, the phone number, the date, the card number and the covered email.
  • No bars with AI off: the name "Jordan Example", the account number 12345678, and the words "Morgan Sample" and "client code BLUE-HERON-4471" in the covered line.
  • With AI on (English model): 7 bars. The AI added bars on "Jordan" and "Morgan Sample". "Example", 12345678 and "client code BLUE-HERON-4471" still had no bar.

So automatic detection did not find all the private text on this page, with or without AI. With AI off, we typed "12345678, Jordan Example" in Always hide these words and dragged one bar over the black rectangle. All of these words then had a bar. We downloaded the new PDF and examined it:

  • pdftotext found no text.
  • A search of the raw bytes found none of the made-up data that we searched for.
  • pdfimages listed one image, and pdfinfo showed one page. The original title and author were gone. The file shows the Creator and Producer of the tool.
  • The Redaction Checker showed "1 page checked · no leaks found. Look at the points to check below." Its points to check were the Creator, the Producer and the dates in the new file.

The browser log shows only GET and HEAD requests in this test, so neither tool sent an upload request.

What we did not test

  • Adobe Acrobat and Preview. The steps for these apps come from the vendor pages, and we have no test result for them.
  • Real documents, documents with many pages, and files from other PDF apps. All test files came from one script, and each has one page.
  • Comments, form fields, attachments and earlier saved versions.
  • Other browsers, and text in other languages.

This is one test of one kind of file. It does not show how often the tools find private text in other files.

How to test your own PDF

  1. Copy the area. Open the file in a PDF reader, select the text around each black bar, and paste it into a text editor. If you see the hidden words, the file is not safe to share.
  2. Open the file in the Redaction Checker. Your file stays on your device or secure network and never touches our servers.
  3. Read the findings. Leaks show first, then points to check. Look at the metadata too.
  4. Fix each leak. Use a redaction tool on the original file, then test the new file again.
  5. Read each page yourself. "No leaks found" means only that the checks found no leaked text. It does not mean that all private details are hidden.

To see a failed result first, click Try a badly redacted example in the Redaction Checker. If you have pdftotext, you can also run pdftotext your-file.pdf - to print the text in the file.

How do you black out text in a scanned PDF?

A scanned page is a picture. It has no text that the PDF Redactor can read, so you must draw the bars by hand. We made a picture-only PDF from the same letter to test this. The tool showed:

1 page. This PDF has no text that can be read, so it is probably a scan. Drag on a page to add a black bar.

The tool added no bars at the start, and a word in Always hide these words added no bar. We dragged one bar over the private line and downloaded the file. The line was black in the new file, and pdftotext found no text. So read each page, and drag a bar over each private item, including a signature or a handwritten note.

The Redaction Checker cannot tell you what a picture shows. We opened the picture-only PDF with the private line not covered, and it showed "no leaks found". Only you can check a scanned page.

Some scan files also have invisible text from OCR (software that reads text in an image). We made one test file of this type:

  • The PDF Redactor read the invisible text and added 6 bars at the start. After we dragged a bar and downloaded the file, pdftotext found no text in the new file. Still read the page and drag bars by hand, because OCR text can be different from the picture.
  • The Redaction Checker showed "no leaks found" on this file, but pdftotext printed the invisible text. A clean result does not show that a scan has no text layer.
  • When we added a black rectangle over the private line in a copy of this file, the Redaction Checker found "Text under black bars". The black rectangle hid the line on the page, but the OCR text was still in the file.

For more about a file that starts in Word, read how to redact in Word.

Black out text in a PDF