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Password-protect or unlock a PDF

Lock a PDF with an AES-256 password and permissions, or remove a password you know, using encryption that runs in your browser.

Drop a PDF to protector click to browse · add a password and permissions
Choose PDFProcessed on your device — never uploaded
Runs in your browser · no uploadHow it works

How to use Protect or unlock PDF

  1. 1

    Add the PDFs

    Drop up to 10 PDF files of up to 50 MB each. A file that is already protected asks for its current password.

  2. 2

    Type a password twice

    The meter rates it from Weak to Strong; 12 or more characters mixing letters, digits and symbols reach Strong.

  3. 3

    Restrict readers if you want

    Switch on Restrict what readers can do to block printing, copying, editing or comments, with an optional permissions password.

  4. 4

    Protect and download

    Press Protect PDF and save each locked file, or all of them as one ZIP. Store the password somewhere safe.

Limits and Pro

Up to 10 PDFs per batch and 50 MB per file, with AES-256 or AES-128 encryption at no cost.

Pro protects up to 500 PDFs at a time, each up to 4 GB. See Pro

About Protect or unlock PDF

Protect PDF writes an encrypted copy of each document, named like contract-protected.pdf. With the default AES-256 setting every page, image and attachment in the file is encrypted with a key derived from your password, using the scheme Acrobat X introduced and the PDF 2.0 standard adopted; AES-128 is available for software from before 2010, and the old RC4 method is not offered at all. Nothing else changes: text, fonts, bookmarks, links and form fields are exactly as they were, and the file size barely changes, since each encrypted stream only gains a few bytes of padding.

A PDF can hold two passwords. The open password keeps the content private, because the file can't be read without it. The permissions password governs restrictions on printing (high quality, low resolution or not at all), copying text and images, editing pages, and adding comments or filling forms. When you set restrictions without a separate permissions password, the tool generates a random 32-character one, so opening the file never lifts them; accessibility access for screen readers always stays allowed.

Typical uses are payslips, medical letters and contracts sent by email, or a portfolio you share with one client. Restrictions are honoured by mainstream readers but can be ignored by others, so treat them as a courtesy and rely on the open password for secrecy. A forgotten password can't be recovered, and this tool won't sign, redact or watermark a document.

Privacy

Encryption is done by qpdf, an open-source PDF library compiled to WebAssembly, inside a Web Worker in this tab; the 1.3 MB engine is fetched from this site the first time you protect a file. Neither the PDF nor the password you type is sent anywhere, stored or logged, which is also why a lost password can't be reset.

Features

AES-256 encryption

The strongest PDF encryption, supported by Acrobat, Preview, Chrome, Edge and other modern readers. AES-128 is available for old apps.

Permission controls

Allow or block printing (high or low quality), copying text and images, editing, and comments or form filling.

Change a password

Add an already protected PDF, enter its current password and choose a new one.

Several files at once

Protect multiple PDFs with the same password in one go and download them as a ZIP.

Protect or unlock PDF: frequently asked questions

How secure is a PDF protected with AES-256?
The cipher itself has no known practical weakness, so the real protection is your password. Attackers who get the file try guesses offline, and a short or common password falls quickly. A passphrase of four or five random words, or 12 or more mixed characters, puts the file out of reach of guessing. The strength meter warns you when a password is on the common list.
Can I stop people from printing or copying my PDF?
Yes. Turn on Restrict what readers can do and switch off Allow printing, Allow copying text and images, Allow editing, or Allow comments and form filling. Printing can also be limited to low resolution. Acrobat, Preview, Chrome and most other readers obey these settings, but some tools ignore them, so they deter casual copying rather than guarantee it.
What happens if I forget the password?
The file stays locked. Your password never leaves your browser, so no one, including us, has a copy or can reset it, and this tool does not try to crack passwords. Keep the original unprotected file in a safe place, or save the password in a password manager before you send the protected copy to anyone.
How do I change the password on a PDF?
Add the protected PDF, type its current password in the box that appears, then enter the new password twice and press Protect PDF. The old encryption is removed and the new one applied in a single step, so you get one file with the new password. To remove protection entirely instead, use the Unlock PDF tab at the top of the tool.
Will the protected PDF open on phones and Macs?
Yes. AES-256 PDFs open in Adobe Acrobat and Reader, Apple Preview and the Files app on iPhone and iPad, Chrome, Edge and Firefox, and most current Android PDF viewers, which all ask for the password first. Only software released before about 2010 may fail; choose AES-128 under Encryption if the recipient uses something that old.

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