I need to be able to protect PDFs on my Mac from editing BUT allow annotations. We have tried taking the following steps...

We saved a Word doc as pdf on Mac, uploaded it to Adobe Pro, in 'allow changes' chose commenting, filling in form fields, and signing existing signature fields.

We then sent the protected pdf to various devices.

Recipients were prompted to enter a password in order to annotate on Samsung Tablet and Ipad.

Surely, allowing annotation while protecting the pdf from editing is much in demand these days, in particular in the education field where students are receiving pdf worksheets and wish to write their answers using annotation tools on their mobile devices.