How to black out text in a PDF on Mac
The words have to go, not just be covered. Here is how to do it so they are actually gone.
“Blacking out” describes what you see afterwards. What matters is what happens underneath, and there are two completely different things that produce the same-looking page.
| What you do | What you get |
|---|---|
| Draw a filled black rectangle | A page that looks blacked out, with every word still in the file, selectable and copyable |
| Redact the region | A page that looks blacked out, with the content removed from the file |
Only the second one is safe to send.
Redaction is part of Premium, so it carries a small lock in the document actions panel and in the menu bar. The lock is a label rather than a barrier — you can open the feature and see what it does before deciding to unlock it. Reading and every page operation stay free.
Do it properly, step by step
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Work on a copy
Redaction removes content permanently. Keep the original.
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Find every occurrence
⌘+F and search for the name or number. A term that appears once where you noticed it usually appears three more times where you did not. -
Use Redact, not the shapes tool
This is the whole guide in one line. Redact is in the tool pill along the bottom, next to the other markup tools. The rectangle tool sitting next to it does something entirely different.
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Mark the whole region
Not just the part that looks sensitive. Half an account number is often enough to identify the whole one.
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Apply, then verify
Search the result for what you removed. Select across the black areas and try to copy. Both should give you nothing.
Open the blacked-out document, select the area including the black bar, copy, and paste into a plain text note. If words appear, the document is not safe to send. If nothing appears, the content is gone. It takes ten seconds and it is the only check that actually proves anything.
Blacking out on a scan
A scanned page holds no text, so there is nothing to select — which means a rectangle drawn on a scan does hide what is underneath, in the sense that nobody can copy it out. But the original image data may still be present in the file beneath the rectangle, so a drawn box is still the wrong tool. Redact the image region instead: that removes the pixels rather than painting over them.
What else to remove before sending
Blacking out the body is rarely the whole job. Sanitize clears the document's own title, author and keywords, and its comments and marks — the places sensitive information most often survives a careful redaction of the page.
Frequently asked questions
How do I black out text in a PDF so it cannot be read?
Use the Redact tool, not the rectangle. Redaction removes the content; a drawn rectangle only covers it, leaving the text in the file.
How can I tell whether a blacked-out PDF is safe?
Select across the black area, copy, and paste into a plain text note. If words appear, it is not safe. If nothing does, the content is gone.
Can I black out text on a scanned document?
Yes, by redacting the image region, which removes the pixels. A drawn rectangle paints over them and leaves the original image data in the file.
Is blacking out reversible?
A drawn rectangle is — anyone can delete it. A proper redaction is not, which is why you work on a copy.
Do I need to do anything else before sending?
Sanitize the document. Its title, author, keywords and comments are not on the page and often contain exactly what you removed from it.