WrenPDF

Protect PDF

Add an open password to a PDF and restrict printing, copying and editing. AES-256 encryption, entirely in your browser.

What it does

Putting a password on a payslip, medical letter or quote before emailing it means the content stays unreadable even if the file ends up with the wrong person. This tool adds an AES-256 open password: anyone who wants to open the file has to enter it.

You can also stop whoever opens it from printing, copying text or editing. Encryption happens in your browser; neither the file nor the password is sent to a server.

How to use it

  1. Drop your PDF file.
  2. Type a password and repeat it; restrict permissions if you like.
  3. Press "Protect and download".

When is it useful?

  • Emailing payslips and personal documents safely
  • Protecting quotes and contracts sent to clients
  • Keeping sensitive archived documents behind a password
  • Locking files placed in shared folders against casual reading

Tips

  • Never send the password in the same email as the file; share it by phone or message.
  • Use at least 12 characters mixing letters, numbers and symbols; "Suggest a strong password" creates one for you.
  • Keep an unencrypted copy of the original somewhere safe.

Frequently asked questions

Which encryption is used?
AES-256 (PDF 2.0, revision 6). Adobe Acrobat, Chrome, Edge, macOS Preview and every current PDF reader can open it.
What if I forget my password?
The file cannot be opened and there is no way to recover the password. Note it somewhere safe and keep the original file.
Is my password sent anywhere?
No. The password and the file are used only in your browser's memory; nothing is sent to a server or stored.
What do the permissions do?
They stop whoever opens the file from printing, copying text or editing. Readers are expected to honour these limits; the real protection is the open password.
Can I open the protected PDF on my phone?
Yes. The built-in PDF viewers and browsers on iPhone and Android open AES-256 protected PDFs with the password.
Can I add a new password to a PDF that already has one?
Remove the current password with Unlock PDF first, then protect the file here with the new one.

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