Use Preview’s real Redact tool, not a black box, before you share a PDF from your Mac. A black box can hide text from your eyes, but the text may still be copied, searched, or recovered. Preview’s Redact tool removes the selected content from the file when you save it. That is the bit that matters.

TLDR: Open the PDF in Preview, make a copy, turn on the Markup toolbar, choose Redact, cover the private text, then save the redacted copy. For example, if you send a lease to a new roommate, hide your Social Security number, bank info, and old address first. In a small office, even one PDF with 3 exposed account numbers can cause a very annoying afternoon. Search the finished PDF for the hidden words before you send it.

Why redaction is not the same as “covering it up”

Redaction sounds fancy. It is not. It means removing information so nobody else can see or recover it.

Here is the classic mistake. You open a PDF. You draw a black rectangle over a credit card number. You smile. You send it.

Then someone selects the area, copies it, and pastes the number into Notes. Surprise. The number was still there.

Honestly, it feels like the computer is being petty. But it is doing what you told it to do. You added a shape. You did not remove the text.

Preview on Mac has a proper redaction feature. Use that instead.

Before you start: make a copy

Redaction is meant to be permanent. That is good. It is also dangerous if you redact the only copy.

So do this first:

  1. Find your PDF in Finder.
  2. Right click the file.
  3. Choose Duplicate.
  4. Rename the copy something clear, like Contract redacted.pdf.

Keep the original safe. Work on the copy. Future you will be grateful.

How to redact a PDF in Preview on Mac

Now for the clean, simple path.

  1. Open the copied PDF in Preview.
  2. Click the Markup button. It looks like a pen tip inside a circle.
  3. Find the Redact tool. It may look like a solid black rectangle or a marked text icon.
  4. If you do not see it, click Tools in the menu bar, then look for Redact.
  5. Drag over the text or area you want to remove.
  6. Repeat for every private item.
  7. Save the file when you are done.

Preview usually warns you that redaction is permanent after saving. Good. That warning is your friend. It means the tool is doing real work.

The redacted area will show as a dark block. The original text should be gone, not just hidden behind a costume.

What should you redact?

Start with anything that could identify you, cost you money, or cause trouble.

  • Social Security numbers
  • Tax ID numbers
  • Bank account numbers
  • Credit card numbers
  • Medical record numbers
  • Client names
  • Home addresses
  • Phone numbers
  • Email addresses
  • Signatures
  • Barcodes and QR codes
  • Case numbers or claim numbers

Do not forget headers and footers. That tiny text at the bottom of page 7 loves to ruin your day.

Redact images too

PDFs are sneaky. Some private data is not text. It may be part of an image.

Think of a scanned passport. Or a photographed bill. Or a signed form. You cannot search that text, but people can still read it.

Use the Redact tool over those areas too. Drag over the face, number, signature, or address. Treat it like putting a digital sticker over the private part, then burning the sticker into the file.

That image is a little dramatic. But you get the point.

How to check your redaction

Do not trust your eyes only. Test the file.

  1. Save the redacted PDF.
  2. Close it.
  3. Open it again.
  4. Press Command + F.
  5. Search for a word or number you redacted.
  6. Try to select text around the black box.
  7. Copy and paste that area into TextEdit or Notes.

If the private text appears, stop. The redaction failed or you used the wrong tool.

If the search finds nothing, that is a good sign. Still scan every page before sending. Expect to waste time on page checks when the PDF has lots of tiny form fields. It is boring. It is also much better than sending your tax number to twelve strangers.

Do not use these tools for real redaction

Preview has many markup tools. Some are useful. Some are traps if you care about privacy.

Avoid these for sensitive info:

  • Shapes: A black rectangle may only sit on top of the text.
  • Highlight: This calls attention to the thing you meant to hide. Truly wild.
  • Text boxes: They add more content. They do not remove old content.
  • Drawing tools: Scribbles can look solid but still leave data underneath.
  • Crop: Cropping can hide edges, but hidden page content may remain in some files.

The Redact tool is the one you want. If it does not say Redact, be suspicious.

Fast example: sending a pay stub

Say you need to send a pay stub to a landlord. They need to see your name, employer, and income. They do not need your full bank account number.

Here is a safe plan:

  1. Duplicate the PDF.
  2. Open the copy in Preview.
  3. Redact your employee ID.
  4. Redact any account number.
  5. Redact your full Social Security number if it appears.
  6. Leave only the details the landlord asked for.
  7. Search the file for the hidden numbers.
  8. Send the redacted copy.

This takes about 2 minutes for a one page document. It can save hours of cleanup later.

What about metadata?

Redaction removes the visible content you select. But PDFs can also contain metadata. That may include author name, app name, creation date, or comments.

Preview is not the best tool for deep PDF cleaning. If the PDF is highly sensitive, use a trusted PDF security tool or ask your legal, HR, medical, or IT team. Annoying? Yes. Worth it? Also yes.

For casual use, you can reduce risk by creating a fresh PDF after redaction:

  1. Open the redacted PDF.
  2. Choose File, then Print.
  3. Click the PDF menu.
  4. Choose Save as PDF.
  5. Save it with a new name.

This can help flatten some content. Still, do not treat it as magic. Check the result again.

Common mistakes to avoid

  • Redacting the only copy: Always duplicate first.
  • Missing repeated info: Search for the same number across the whole PDF.
  • Forgetting attachments: Some PDFs include extra files or pages.
  • Sending too soon: Reopen and test before sharing.
  • Trusting screenshots: Screenshots can work for simple sharing, but quality drops and mistakes happen.

Best sharing tips after redaction

Once the PDF is clean, share it with care.

  • Use a clear file name, like Invoice redacted.pdf.
  • Send it only to the right person.
  • Use a secure portal when possible.
  • Avoid public links for private documents.
  • Delete extra draft copies if you no longer need them.

Also, slow down for 20 seconds before you hit Send. Open the attachment from the email draft. Make sure it is the redacted version. Not the original. Not the “final final real one” from last Tuesday.

The simple rule

If someone should never see it, use Redact. Not a rectangle. Not a scribble. Not a crop.

Preview makes basic PDF redaction easy once you know where the button is. Make a copy. Redact the private bits. Save. Reopen. Search. Then share.

That small habit can keep your money, identity, clients, and sanity safer.