A password on a PDF means the file is encrypted: without the password, a reader cannot display it at all. That is useful when the file goes out by email, sits in a shared folder or travels on a USB stick.
How strong is the protection?
The PDF is encrypted with 256-bit AES, the strongest encryption in the PDF standard, supported by every current reader including Adobe Acrobat, Preview on the Mac and browser PDF viewers. The protection is only as good as the password. A short word from the dictionary can be guessed by software; a long passphrase of four or five unrelated words cannot, in practice.
Send the password through a different channel from the file. If both go in the same email, anyone who reads the email can open the PDF.
What happens if I forget the password?
You will not be able to open the protected copy, and neither can we. Keep your original, unprotected file somewhere safe, or store the password in a password manager.
Does the file leave my computer?
On this page the encryption runs in your browser. The unencrypted PDF is never uploaded, so the file never leaves your device. That matters most for exactly the kind of document you would want to protect.
Does it change the document?
Only the encryption layer is added. Pages, text, images and links are unchanged, and the file size stays almost the same.
What are the limits?
Free covers PDFs up to 50 MB, with no daily cap. Pro covers files up to 500 MB. Protecting payslips or reports one by one is slow; the pipeline builder can put the same password on a whole set in one run. You can try a pipeline on up to 3 files for free.
How to password-protect a PDF
- Drop your PDF onto the drop zone.
- Type the password, and choose whether readers may print and copy text.
- Click Protect.
- Download the protected PDF and test that it asks for the password.
FAQ
Can I remove the password later?
Yes, if you know it. Use Unlock PDF and enter the password to save an unprotected copy.
Does the password stop people from printing or copying?
Printing is allowed and copying text is blocked by default; you can change both. These permissions are respected by mainstream readers, but they are a request rather than a lock once someone has opened the file.
Can I protect a PDF that already has a password?
Unlock it first with the current password, then protect it with the new one.
Will the protected PDF open on phones?
Yes. The iOS and Android system viewers and common PDF apps all ask for the password and open AES-encrypted files.