Password protect a PDF
Add a password to a PDF so only people you share it with can open it. Files are encrypted with AES-256 using qpdf, a long-established open-source PDF library, entirely on your device.
or drop a file here
One PDF, up to 250 MB.
Processed on your device. Nothing is uploaded.
How to password protect a PDF
Open the PDF
Choose the document you want to protect.
Set a password
Type it twice. A strength meter helps you choose a good one.
Set permissions (optional)
Decide whether readers may print, copy or edit.
Encrypt and save
Download the protected PDF and share the password separately.
Key features
AES-256 encryption
The strongest encryption the PDF standard supports, readable by Adobe Acrobat, Preview, Chrome, Edge, Firefox and other modern readers.
Audited, not home-made
Encryption is performed by qpdf compiled to WebAssembly. We don’t write our own cryptography.
Password never leaves your device
Your password and document are processed in the browser and never sent to PDF365.
Optional permissions
Ask readers’ software to disallow printing, copying or editing.
Choosing and sharing a password
Encryption is only as strong as the password. Use at least 12 characters, or three or four unrelated words, and avoid names, dates and anything easy to guess. Never send the password in the same email as the file: use a text message, a phone call or a password manager’s sharing feature.
Permissions (no printing, no copying) are honoured by mainstream readers but are not enforced by the encryption itself. Treat them as a polite instruction. For more on keeping documents private, read our PDF privacy guide, or see how to password protect a PDF on Mac and Windows.
Security and privacy
Protect PDF runs entirely in your browser. Your file is processed in this tab’s memory and never uploaded to PDF365 or anyone else. When you close the tab or press “Start over”, the data is discarded.
Because the password is never sent anywhere, we cannot recover it for you. If you forget it, the file cannot be opened. Store it in a password manager.
Read more in our privacy policy.
Questions about Protect PDF
How secure is AES-256?
With a strong password, AES-256 is considered secure against brute-force attack. The weak point is almost always a short or guessable password.
Can I remove the password later?
Yes, with Unlock PDF, as long as you know the password.
Will it open on phones?
Yes. iOS, Android, and modern desktop readers all support AES-256 encrypted PDFs.
What is the permissions password?
An optional second password that lets its holder change the permissions. If you leave it blank, a long random one is generated and immediately discarded, so the permissions can’t be changed without removing encryption.