Protect PDF
Add a password required to open one PDF.
Protected locally in your browser. Your PDF and password are not uploaded.
or drop it here
One PDF. Up to 40 MB and 200 pages. These are safety ceilings.
A short password is easier to guess. AES-256 does not make it stronger.
Your PDF is protected
A password is required to open the download. The password is not shown here.
- File name
- pdfzaro-protected.pdf
- Pages
How it works
You choose one unencrypted PDF and one password. PDFZaro encrypts the file in your browser with AES-256. The download is one PDF named pdfzaro-protected.pdf. A password is required to open it.
Privacy
The PDF and the password stay on this device. They are not uploaded. The password is not put in the page address, analytics, or the downloaded file name.
Limits
One PDF, up to 40 MB and 200 pages. These are safety ceilings, not a statement about every phone or computer.
What this tool does not do
- It does not stop someone who knows or guesses the password.
- AES-256 does not make a short password strong.
- It does not block printing, copying, or screenshots after the file is opened.
- It does not remove scripts, form data, or attachments.
- It does not keep a digital signature valid, and it does not claim PDF/A conformance.
- A file that is already encrypted is rejected. This page does not change or remove a password.
- The signature check looks for a marker. Some signed files do not show that marker.
Related tools
Questions
Are the PDF and password uploaded?
No. Protection runs in your browser. The site does not receive the file bytes, the file name, or the password.
What encryption is used?
AES-256. A password is required to open the PDF.
Can I ban printing or copying?
No. Those restrictions depend on the reader and are not a lock. This tool only adds a password required to open the file.
Can I unlock a PDF or change its password?
No. A PDF that is already encrypted is rejected.
Why is a signed PDF rejected?
Encrypting it would break the signature. PDFZaro refuses a file when it sees a signature marker, and it does not offer to continue. Some signed files do not show that marker.
How long can the password be?
Up to 127 UTF-8 bytes. That is not the same as 127 characters. Some letters and emoji use more than one byte.