Protect PDF
Password-protect a PDF with AES encryption.
Free · No sign-up · Files deleted in 1 hour
How to Protect PDF
- Upload your PDFDrag it in or import from Drive / OneDrive.
- Set a passwordChoose encryption strength and optional permissions, expiry and watermark.
- DownloadEncrypt and save — processed privately, deleted automatically.
Password Protect PDF Online — AES-256 Encryption, Free
Lock a PDF with a password and AES-128 or AES-256 encryption, right in your browser — set the password people need to open the file, plus an optional owner password — a random one is used if you leave it blank, which is what makes the permissions hold — that controls what they can do once they're in.
Permissions go beyond a blanket lock: set printing to full, low-resolution-only or none, and modification to none, form-filling, annotating, assembly or full editing. Mainstream readers honour all of it — but PDF permissions are instructions to the reader rather than a cryptographic lock, so treat them as a deterrent for people who already have the password, not a guarantee. The encryption itself is what keeps the file from everyone else.
Encryption, permissions and watermark are all applied in one pass — no separate steps, no sign-up. Files are processed securely and deleted automatically after an hour, so a sensitive document never sits around after you've downloaded the protected copy. Encryption works on documents up to 50 MB.
- AES-128 or AES-256 encryption
- Separate open and owner passwords — a random owner password if you leave it blank
- Granular print & modify permission levels, plus a copy toggle
- Optional dated notice and confidentiality watermark, stamped on every page
- No account needed; the protected file clears after an hour
Frequently asked questions
How do I password-protect a PDF for free?
Upload your PDF, set an open password (and optionally a separate owner password), choose AES-256 or AES-128 encryption, and download — free, with no sign-up.
What's the difference between the open password and the owner password?
The open password is what someone needs to view the PDF at all. The owner password is what's needed to change the permissions afterwards — printing, copying, modifying. Leave it blank and a random one is used, which is what stops recipients simply removing the restrictions; the trade-off is that you can't change them later either, so set your own if you need to.
Can I let people view a PDF but stop them printing or copying the text?
You can set print permission to "None" and switch off "Allow copying text", and every mainstream PDF reader will honour that. Be clear on what it is, though: PDF permissions are instructions to the reader, not a cryptographic lock — anyone you give the open password to can strip them with freely available tools. The encryption genuinely protects the file from people who don't have the password; the permissions are a deterrent for the people who do.
Is it safe to upload a sensitive PDF online just to add a password?
Dudle processes the file over an encrypted connection and deletes both the upload and the protected result automatically after an hour — no account is created and nothing is kept longer than that.
How do I remove a password from a PDF I already own?
This tool only adds protection, it doesn't remove it — if you know the current password, most PDF readers (Preview on Mac, Adobe Acrobat) can open the file and save an unlocked copy directly.