cannot remove security on my document when signed or certified

I have created a security password for my documents that disallow copying/editing, but allow hi-res printing, permission for screen readers and allows commenting.

I need to make a change and remove the security, but I get an error that says "You cannot change security on this document because the document is signed or certified."

This password policy has been used for years and was never a problem removing security before. How can I correct this so that I have the ability to remove the security (with password) at a later date?

I am not intentionally signing or adding a certificate to my document. If this is a setting somewhere, how do I disable it?