Password protection

Open File → Password protection… or Protect → Password protect. The saved PDF is encrypted with AES-256 (PDF 2.0 encryption).

1. Turn on Require a password to open the document and enter the Open password twice, and/or
2. Turn on Restrict printing, editing and copying, enter a Permissions password twice, and choose what’s allowed without it:
   • Printing, High-quality printing
   • Changing the document
   • Copying text and images
   • Commenting
   • Filling in form fields
   • Text access for screen readers
   • Inserting, deleting and rotating pages
3. Choose Apply (protect the next save) or Apply & save.

While protection is on, a lock icon appears next to the file name and every PDF you save from this document is encrypted, including extracted pages and split parts. To stop, open the dialog again and choose Remove protection.

Permissions are a request, not a lock

PDF viewers are expected to enforce the restrictions, but they can’t stop someone who can open the file from using software that ignores them. For confidential documents, rely on the open password.

• The permissions password must be different from the open password; otherwise anyone who can open the file could lift the restrictions.
• If you only set an open password, a random permissions password is used, so nobody can change the (unrestricted) permissions.
• Passwords can’t be recovered. Keep them somewhere safe.
• Current versions of Acrobat, Preview, Chrome, Firefox and pdf.js open AES-256 files. Very old readers that only support RC4 or AES-128 can’t.
• Opening a protected PDF in the editor asks for its password. Pages from protected files are turned into images when you save.