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How to password-protect a PDF (and share the password safely)

Encrypt a PDF so only the right person can open it, choose a password that holds up, send it without leaking it, and remove it again later.

· 2 min read

A payslip, a tax form or a scanned ID sent as a plain attachment can be read by anyone who ends up with the email. A password on the PDF means the file itself stays locked, wherever it is forwarded or stored.

Protect the file

  1. Open Protect PDF and drop the document.
  2. Type the password twice.
  3. Decide what the reader may do once it is open: print, copy text, edit.
  4. Click Protect PDF and download the encrypted copy.

The file is encrypted with AES-256, the strongest standard PDF encryption, and opens in Adobe Reader, Preview, and the PDF viewers built into Chrome, Edge and Firefox. It is done in your browser: neither the file nor the password is uploaded.

Choose a password that holds up

The encryption is not the weak point — the password is. Someone who gets the file can try passwords as fast as their computer allows.

  • 12 characters or more, or a passphrase of four or five random words (tulip-orbit-canvas-mild).
  • Not a date of birth, a phone number or a customer number printed in the document.
  • The Password Generator makes both kinds.

Send the password another way

Sending the password in the same email as the file defeats the purpose. Send the PDF by email and the password by text message, a phone call or a messaging app. For documents you exchange regularly with the same person, agree a passphrase once, in person.

What permissions really do

"No printing" or "no copying" are instructions that standard readers respect, not encryption. Anyone who can open the file could still take screenshots or re-type it. Use them to prevent accidents, not to protect secrets — for that, only the open password counts.

Before protecting

  • Remove hidden details. Author names and software information travel with the file; clear them with Edit PDF Metadata.
  • Compress first if needed. An encrypted PDF can't be compressed by most tools afterwards; run Compress PDF before protecting.

Removing the password later

When you receive a protected statement you have to open every month, Unlock PDF removes the password once you type it — useful before merging or archiving. It needs the password; it does not try to guess it.

Tools used in this guide

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