— pdf —
Make text in a PDF truly unreadable (not just a black box)
3 min read
Putting a black box over text does not hide that text, it only lays something over it. The recipient can often just select the text underneath, copy it, or remove the box. Real redaction means removing the text. With PDF redaction the page is rebuilt as an image, so there is no text left to recover. Everything happens in your browser.
You need to black out a national ID number, a salary or a name in a contract before you forward it. The reflex is a black rectangle in Word or a PDF viewer, and done. But that is exactly where it goes wrong: that rectangle sits on top of the text, not in place of it. There are plenty of stories of organisations that published "redacted" documents where you could simply select and copy the text.
The PDF redaction tool does it right. You draw rectangles over what has to go, and the tool actually removes that text from the file instead of covering it.
Why a black box is not safe
A black box you place in Word or as a comment in a viewer is an annotation or drawing on top of the page. The underlying text stays in the file. The recipient only has to delete the annotation, or drag the mouse over the box and copy, and the "redacted" text is back. Search functions, screen readers and indexers also still see that text. It looks removed, but it is not.
Removing text instead of covering it
With real redaction the text is not covered but replaced. PDF redaction rasterises every page you black something out on: that page becomes an image with the black bars baked in. The text layer on that page no longer exists, so there is nothing to select, copy or recover. In the same step the metadata, annotations, form fields and bookmarks are stripped from the whole file, so no hidden traces remain.
Note the trade-off: a redacted page becomes an image, so the text on that page can no longer be selected or searched. Pages where you black out nothing stay untouched.
Step by step
- Open PDF redaction and drop your PDF into the box.
- Drag your mouse over what has to go. Draw multiple rectangles per page if needed; the small cross removes a redaction again.
- Download the redacted PDF. The blacked-out text has then truly left the file.
Checking that it is really gone
Trust is good, checking is better. Open the downloaded PDF and try to search with Ctrl-F for a word you blacked out. If you find nothing, and you cannot select or drag the black bar, the text is really gone. That is the difference with a black box: there your search still finds the text.
Want to remove the invisible data from a file too, such as author and location, read Hidden data in photos and PDFs. And for a copy of your ID you share safely, there is Make a safe ID copy.
Black it out properly: PDF redaction. In your browser, and the text that has to go is really gone.
Frequently asked questions
How do I make text invisible in a PDF?
Not by putting a black box over it, because the text underneath stays in the file. Actually remove the text by redacting the page: draw a rectangle over what has to go, and that page is rebuilt as an image with the black bar baked in. There is then no text left to select or copy.
Can a black box in a PDF be removed?
If the box is an annotation or drawing that sits on top of the text, often yes: the recipient deletes the annotation or selects the text underneath. That is why covering is unsafe. Real redaction replaces the page with an image, so there is nothing to peel away.
Can I still search the text after redacting?
Not on redacted pages; those become an image, so both the blacked-out text and the rest of that page are no longer selectable. Pages without redaction stay searchable. If you want the whole file searchable again, run OCR over the result afterwards.
Is my PDF uploaded?
No. The PDF is loaded and redacted in your browser, and the result goes to your Downloads. Nothing goes to a server. Alongside the boxes you draw, the metadata, annotations and form fields are stripped too.