How to restrict a user from signing a form on Mobile App.

I created a form in Acrobat Pro DC (2015) and I don't want anyone to be able to lock it down with a signature.  Acrobat Reader Mobile allows the user to sign anywhere on the document even when I have removed all of the signature fields.  The form is reader extended, but I would only like to extend the filling of form fields, commenting, saving and printing functionality and not allow signing.  Is this possible?  Please help.