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How to Password Protect a PDF

Written and fact-checked by The EditPDF AI Team

Password-protecting a PDF applies standard encryption so compatible readers ask for a password before displaying the document. EditPDF AI applies AES-256 encryption locally in your browser.

Open password vs. permission flags

PDF encryption controls two separate things, and it helps to know which one you actually need:

  • ·Open password — the document cannot be viewed at all without entering the correct password first
  • ·Permission flags — the document opens freely, but printing, copying, or editing can be restricted for readers who respect those flags

EditPDF AI sets an open password by default and lets you choose between a read-only permission profile or full permissions for readers who already have the password.

Step-by-step: password protect a PDF

  1. 1Open editpdfai.com/pdf-password-lock and upload the PDF you want to encrypt.
  2. 2Enter a password. Use something you can share securely with intended readers — there is no recovery option if it is lost.
  3. 3Choose a permission profile: read-only restricts printing, copying, and editing; full leaves those actions available to anyone with the password.
  4. 4Click Lock PDF. The AES-256 encrypted file downloads automatically.
No password recovery

AES-256 is designed so the file cannot be opened without the correct password — including by EditPDF AI. Store the password somewhere safe before you close the tab.

What AES-256 encryption actually protects

AES-256 is a strong, widely-supported symmetric encryption standard. Once applied, the PDF's content is unreadable to any application that does not have the correct password — this includes PDF viewers, search indexers, and cloud-storage preview generators.

  • ·Encryption happens locally in your browser via a browser-based engine — the unencrypted file is not uploaded
  • ·Permission flags are advisory: compliant readers enforce them, but they are not a substitute for the open password if strong protection is the goal
  • ·Encrypting a PDF does not redact its visible content — anyone who has the password can still read everything on the page

Practical tips

  • ·Share the password through a different channel than the file itself — for example, send the PDF by email and the password by text message
  • ·If you need to remove a password you already know, use Unlock PDF rather than re-uploading the encrypted file elsewhere
  • ·To hide specific sensitive content rather than lock the whole document, use PDF Redactor instead — encryption and redaction solve different problems
Remove a password you already knowDecrypt a PDF you have legitimate access to before editing or merging it.Redact sensitive contentPermanently cover specific text or areas instead of encrypting the whole file.Add a watermark for document controlMark drafts or confidential copies without restricting who can open them.Learn how to redact a PDFCover and verify removal of sensitive information before sharing.
Core PDF tool

PDF Password Lock

The core workflow is available without an account. Browser and tool-specific limits apply.

Password protect a PDF free →

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