Quick answer: To password-protect a PDF, choose it, type a password twice and press Protect PDF. It is encrypted with AES-256, the strongest standard PDF encryption, which every current PDF reader supports; you can also block printing, copying or editing. The PDF and password never leave your device.
Lock a PDF so it only opens with your password, before you email it or send it with a link. Choose whether people who open it may print, copy or edit it.
Protect PDF at a glance
| Price | Free, no sign-up, no watermark, no daily limit |
|---|---|
| Accepts | |
| Largest file | 200 MB per file, several files at once |
| Where it runs | In your browser: files are never uploaded |
| Works on | Any modern browser on iPhone, Android, Windows, Mac and Linux |
| Send the result | Download it, or send it free with a link or by email (up to 20 GB) |
How to protect PDF
- Choose one or more PDFs.
- Type the password that will be needed to open them, twice.
- Untick printing, copying or editing if you want to restrict them.
- Press Protect PDF, then send the file and share the password separately.
Open password and restrictions
- Open password: without it the PDF cannot be opened or read at all. The content is encrypted with AES-256 (PDF 2.0 security), supported by Adobe Acrobat and Reader, Chrome, Edge, Safari, Preview and phone PDF apps.
- Restrictions (printing, copying, editing): honoured by standard PDF readers once the file is open. They are a polite request more than a lock, because some programs ignore them; for truly confidential files rely on the open password.
Choosing and sharing the password
Use a long password, such as three or four random words, and never send it in the same email or chat as the PDF. Send the file by email or with a download link, and the password by text message or phone. There is no way to recover a forgotten password, so keep an unprotected copy of the original.
Encrypted on your device
Encryption runs in your browser with QPDF, a long-established open-source PDF library, compiled to WebAssembly. Neither the PDF nor the password is uploaded. To remove a password later, use Unlock PDF with the password.
How this compares
| This tool | Online converters (e.g. iLovePDF, Smallpdf or Adobe Acrobat online) | Desktop apps (e.g. Adobe Acrobat Pro) | |
|---|---|---|---|
| Your file is uploaded | No | Yes, to their servers | No |
| Install or account | None | Account for some features | Install needed |
| Watermark or daily limits | None | Common on free plans | Depends on the app |
Plans of other services change; check their sites. More pdf tools.
Frequently asked questions
How do I put a password on a PDF for free?
Choose the PDF here, type a password twice and press Protect PDF. The encrypted copy opens only with that password.
How strong is the protection?
The open password uses AES-256, the strongest standard PDF encryption; its real strength is your password, so use a long one.
Can I stop people printing or copying?
Yes, untick those options. Standard PDF readers honour them, but they are not a hard guarantee.
Is my PDF or password uploaded?
No. Both stay on your device.
I forgot the password. Can you remove it?
No. AES-256 cannot be undone without the password, which is the point; Unlock PDF only works when you know it.
Need to send a big file?
Send files up to 20 GB with a download link or by email. Free, no account needed, original quality.
Send large files free