I would like to give the ability to users to password-protect documents when they complete signing them as a web form. Then, they would have to communicate to the sender what the password is. Otherwise, many sensitive items end up in a user's email inbox unprotected.
This should also come along with the ability to assign a field as a password. So there will be a field in the form that's required like, "Social Security Number" that you can enforce the format and this way if I already know my client's social security number, that will automatically be the password. This is very important for using Adobe Acrobat securely.