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Protect PDF – Add a Password to a PDF

Lock a PDF with a password so only people you give it to can open it. The file is encrypted with AES-256, the strongest standard PDF encryption, and you can also choose whether readers may print, copy text or edit. Everything happens in your browser — the file and password are never uploaded.

Your files stay on your device

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How to protect a PDF with a password

  1. Choose your PDF.
  2. Type a password and type it again to confirm.
  3. Choose what people who open the PDF may do: print, copy text and images, edit and fill in forms.
  4. Press Protect PDF and download the protected file.

Choosing a strong password

  • Make it long — 12 or more characters, or a phrase of four random words.
  • Avoid personal details such as birthdays or names that are easy to guess.
  • Use a new password rather than one you use for email or banking.
  • Generate one with the password generator and store it in a password manager.

Sharing protected PDFs safely

  • Send the password separately, by a different channel — a phone call, text message or chat — not in the same email as the file.
  • Agree a password scheme with regular contacts, such as accountants, so you don’t have to send passwords each time.
  • Don’t rely on permissions for confidential content; anyone with the open password can read the document.

When to protect a PDF

  • Personal documents: passports, ID, payslips, bank statements, tax returns and medical records.
  • Business documents: contracts, salary letters, invoices and financial reports.
  • Client files: legal, accounting and HR documents sent by email.
  • Exam papers and answer keys before they’re released.

Many data protection laws, such as the GDPR, expect personal data to be protected appropriately when shared; encrypting attachments is a simple step.

Permissions explained

PermissionWhen unticked
PrintPrinting is blocked
Copy text and imagesSelecting and copying is blocked
Edit, comment and fill in formsChanges, comments and form filling are blocked

Readers with accessibility software can still read the text aloud.

Protecting several files

To send several documents under one password, combine them first with merge PDF and then protect the merged file. Recipients only have to enter the password once, and the documents stay together in the right order.

Older PDF readers

AES-256 is supported by every PDF reader released in the last fifteen years or so. If a recipient uses very old software and can’t open the file, ask them to update their reader or open it in a web browser.

Privacy

Encryption is done in your browser using a well-tested open-source PDF library. Your PDF and password never leave your device.

To remove a password later, use unlock PDF. To mark a document as confidential on every page as well, add a watermark.

Frequently asked questions

How do I password-protect a PDF?

Choose the PDF, type a password twice, choose what readers may do, and press “Protect PDF”. Download the protected file and share the password separately — for example by phone or text message rather than in the same email.

How secure is it?

The PDF is encrypted with AES-256. With a long, unpredictable password, the contents can’t practically be read without it. A short or common password can be guessed, so use at least 8–12 characters.

What do the permission options do?

They ask PDF apps to block printing, copying or editing. Most apps respect them, but some software ignores permissions. Only the open password truly protects the contents.

What if I forget the password?

The file can’t be recovered — not by us or anyone else. Keep the password in a password manager and keep an unprotected copy somewhere safe.

Can I protect a PDF that already has a password?

Unlock it first with the unlock PDF tool, then protect it again with the new password.

Will the recipient need special software?

No. Any modern PDF reader — browsers, Adobe Acrobat Reader, Apple Preview and phone apps — opens AES-256 encrypted PDFs after the password is entered.

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