How to lock a pdf from editing without adobe acrobat?

pdftk is a free (GPL-licensed), classic command-line tool for PDF manipulation that you can lock a pdf from editing on Windows. It has a simple syntax specifically for applying an "owner password" that restricts actions like editing. It fits your requirements because it's not the software you mentioned.

How it works: You use the owner_pw parameter to set a password that controls permissions. To completely lock a pdf from editing, you simply omit any allow permissions.

Basic Command:

batch

pdftk input, pdf output locked, pdf owner_ pw "YourOwnerPassword"

This will create locked.pdf. When someone opens it, they will not be able to edit, copy, or print the content because no permissions are granted.

For the most restrictive lock (no printing, no copying, no editing):

batch

pdftk input, pdf output locked, pdf owner_pw "YourOwnerPassword" allow

By providing an empty list of allow permissions, you explicitly disallow all actions.

Important caveat: This method relies on the PDF viewer to respect the security settings. While effective for most casual users, it is not a super-secure, military-grade protection, as the specification itself notes that compliant software could be modified to ignore these flags.