Password Protect a PDF, Free Online
Password protect a PDF free online with AES-256, the strongest encryption PDFs support. Anyone opening it will need the password — and the file is encrypted on your device, never uploaded.
Fit Meter
Settings appear once you add a PDF.
Advanced 5
Guards the permissions above. Left empty, a long random one is used so nobody can lift them.
Still going. Your own device is doing this, so a long scan or a big batch takes as long as it takes — and none of it is being uploaded.
Bytes of your files sent anywhere: 0 B · nothing leaves this tab
Every request this page makes is listed as it happens. You’ll see our own code loading, and for some formats a codec engine, but never your file going out.
- Waiting for network activity…
Check it yourself: open your browser’s developer tools on the Network tab, or turn off Wi-Fi once the page has loaded. The tools keep working.
How to password protect a PDF free online
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Add your PDFs
Drop the PDF you want to lock.
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Check the settings
Type a password twice. Under Advanced, choose whether people who open it may print, copy or edit.
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Save the result
Save the encrypted copy. Every PDF reader will ask for the password before showing a single page.
Why it doesn’t upload
Encrypting a PDF on a website means sending the unencrypted file and your chosen password to that website — the one moment it’s least protected. Here the encryption runs on your device with qpdf, so the unlocked document never travels anywhere.
Check it in your browser’s Network tabWorth knowing
- Forget the password and the file can’t be opened — by you or by us. There is no reset.
- Permissions (no printing, no copying) are honoured by mainstream readers but aren’t encryption-strength: some tools ignore them. The open password is what really protects the file.
- A short password can be guessed by brute force. Use at least 8 characters, or a few unrelated words.
- Encrypting invalidates existing digital signatures.
Under the hood
What happens to your file
qpdf, the reference implementation of PDF encryption, writes the file with AES-256 (the PDF 2.0 security handler) and the permissions you choose. The password never leaves the page; it is used once to derive the key and then discarded. A viewer can open the result only with the password.
Reference: qpdf manual · NIST FIPS 197 (AES) · ISO 32000-2 (PDF 2.0)
Questions
How do I password protect a PDF for free?
Drop it here, type a password twice and press Encrypt PDF. The locked copy uses AES-256 and asks for the password in Adobe Reader, Preview, Chrome, Edge and every other current reader.
How strong is AES-256 PDF encryption?
It’s the strongest the PDF standard offers and can’t be broken by trying keys. The weak point is always the password itself — a long one is effectively uncrackable, a short common one isn’t.
Can I stop people printing or copying my PDF?
Yes, under Advanced. Readers like Acrobat and Preview honour these settings, but they’re a request rather than a lock — for real control, rely on who knows the open password.
Will the password work on a phone?
Yes. iPhone, iPad and Android PDF viewers all open AES-256 encrypted PDFs and ask for the password.
Is my password sent anywhere?
No. The password and the file stay in your browser tab. Nothing is uploaded, and nothing is stored after you close it.
Read more about this
More security & privacy tools
All security & privacy tools- Remove PDF Password Open a locked PDF once with its password and save a copy that opens without it.
- Unlock PDF Restrictions Remove print, copy and edit restrictions from a PDF you own.
- Redact PDF Black out text for good — the words underneath are removed, not covered.
- Remove PDF Metadata Strip the author, software, dates and hidden XMP before you share.