How to use it

Choose or drop the PDF you want to protect.
Enter the password twice.
Optionally open Encryption and permissions to restrict printing, copying or editing, or to choose AES-128 for very old readers.
Select Protect PDF and download the encrypted copy.

How it works

The tool encrypts the PDF with the standard PDF security handler using the open-source @cantoo/pdf-lib library. By default it uses AES-256 (security handler revision 6, as defined in PDF 2.0), which Adobe Acrobat X and later, current browsers and most modern readers open. AES-128 is offered for readers older than about 2010.

The open password (user password) encrypts every text, image and font in the file. Without it the content cannot be read. Permissions such as no printing or no copying are flags stored next to the encryption; well-behaved readers enforce them, but they are not a technical barrier for someone who can open the file, so do not rely on them for confidential material.

Files that are already encrypted are refused: remove the old protection first. Digital signatures in the original become invalid, because encrypting rewrites the file. File size and page content stay the same apart from small overhead. How large a file you can protect depends on your plan.

Examples

Sending a payslip by email

Protect payslip-march.pdf with a password you share by phone. The email attachment can only be opened by someone who knows the password.

Read-only handout

Set a password, then untick copying and editing and set printing to low resolution. Readers that respect permissions will let recipients view the handout but not copy its text.

Frequently asked questions

How strong is the protection?

With AES-256 and a long, unique password the content cannot practically be decrypted without the password. A short or common password can be guessed by cracking software, so the password is the weak point, not the algorithm.

Do the printing and copying restrictions really stop people?

Only in readers that respect them, which includes Acrobat and most common viewers. Some software ignores the flags, so anyone who can open the file may still be able to print or copy. Use them as a polite barrier, not as security.

I forgot the password. Can you recover it?

No. The password is never stored or sent anywhere, and this site does not crack passwords. Keep your original unprotected file, which this tool does not change.

Why is my PDF refused as already encrypted?

It already has a password or permission restrictions. Remove them first with Unlock PDF (you need the password), then protect the unlocked copy with your new settings.

Will the protected file open on phones?

Yes, current iOS and Android viewers, browsers and Acrobat open AES-256 PDFs and ask for the password. If a very old reader cannot open it, protect the file again with AES-128.

Privacy

The PDF and the passwords stay in your browser: the file is read, encrypted and offered for download with JavaScript on your device. Nothing is uploaded or stored, and passwords are not included in analytics; only an anonymous event that the tool was used is counted.