Before you send a tax form, a bank statement or a lease application, you may want to hide private details. Things like your Social Security number, your bank account number or a child's name. This is called redacting.
Here's the problem: lots of ways of "blacking out" a PDF don't really hide anything. This guide shows you how to do it properly, for free, and how to check your work. The easiest safe option is TrueRedact, which works right in your browser.
The big mistake: black boxes and highlighters
Many people open a PDF, draw a black rectangle over their SSN, and save it. It looks hidden. But in most PDF programs, that box is just a shape sitting on top. The number is still in the file underneath.
Anyone who gets the file can often:
- Select the black area and copy the words out.
- Search the file for the number.
- Move or delete the box.
A black highlighter does the same thing. So does printing to PDF in some cases, because the words stay as text.
Real redaction deletes the words from the file. Then the black box just shows where something used to be.
Method 1: TrueRedact (free to try, nothing is uploaded)
TrueRedact removes the words from the file, not just covers them. It runs inside your web browser, so your document never leaves your device.
- Go to tools.ltd/trueredact.
- Click the big button and choose your PDF.
- TrueRedact already looks for Social Security numbers, account numbers, emails and phone numbers. Names are not found on their own. Type each name or word you want hidden.
- Check the preview. Make sure every spot you want hidden is marked.
- Click to hide them. TrueRedact checks the new copy, then you download it.
- Do the safety test below.
TrueRedact can't read words inside a photo or a scan. If your PDF is a scan, use Method 2 or Method 3.
Method 2: Print and scan (free, no software)
This old-fashioned way works if you're careful.
- Print the document.
- Cover the private details fully with a thick black marker. Go over it twice.
- Hold the page up to a light. If you can still read the numbers, cover them again, or use tape and paper.
- Scan the page back into a PDF.
Because the scan is a picture, the hidden words aren't in the file at all. The downside: it's slow, the file looks less sharp, and the text can't be searched.
Method 3: Paid PDF software
Programs like Adobe Acrobat Pro have a proper Redact tool. The key is to use the redact tool, not the drawing or comment tools, and to apply the redactions before saving. Until you click Apply, the words are still there.
Some newer versions of Preview on Mac also have a Redact option in the Tools menu. Don't use the shape or highlight tools for this.
The safety test (do this every time)
Whatever method you use, check the saved file before you send it.
- Open the new redacted file, not the original.
- Press Ctrl + F (Windows) or Command + F (Mac) and search for the hidden number or name. It should find nothing.
- Drag your mouse across the black area and copy it.
- Paste into Notepad (Windows) or TextEdit (Mac). Nothing private should appear.
- Press Ctrl + A or Command + A to select all text on the page. The hidden spot should not light up with words.
If any test fails, don't send the file. Redact it again with a real redaction tool.
More tips
- Keep the original. Save the redacted copy with a new name, like "Lease application - redacted."
- Check every page. Your SSN might show up on page 1 and again on page 6.
- Only send what's needed. If they only need one page, remove the rest with PageKit first.
- Don't forget the file name. "John Smith SSN 123..." in a file name defeats the point.
Frequently asked questions
What does redact mean?
It means removing private details from a document, like a Social Security number, so no one else can read them.
Is a black box the same as redacting?
No. A black box drawn on top often leaves the words underneath. Someone can copy them out. Real redaction deletes the words from the file.
Does TrueRedact upload my file?
No. TrueRedact works inside your web browser, so your PDF stays on your computer.
How can I check my file is safe?
Open the saved file, select the blacked-out area, copy it, and paste it into a plain note. If any words appear, it isn't safe.
Related guides: Black box on PDF not hiding text? · PDF too big to email · More redaction guides