How to create a mandatory Yes or No answers by using Radio Buttons

Mandatory in what sense? Although a field can be marked as required, this will only be enforced when submitting the form (either by email or to a web server). But it doesn't really apply to radio buttons or check boxes, since they always have a value, either their export value or "Off" if none in the group are selected. You cannot prevent the user from saving an incomplete form, but you can add scripting that will prevent them from continuing with the form until an item is selected in a radio button group.

Your suggestion is perfect! Thank you! Although, once again, I have no experience with JavaScripting. My thought:

If the Yes & No fields are left blank, and the client clicks on the SAVE button, a message would pop up andstate that you must complete one of the two options; and direct them back to that particular Yes/No question.Any scripting that you could provide would be really appreciated!!

So let's say the name of your radio button group is "Radio Button1". You can then add this script as the WillSave action of your file (it will NOT prevent the file from being saved, as previously mentioned):

if (getField("Radio Button1").value=="Off") {
app.alert("You should select either Yes or No!",3);
getField("Radio Button1").setFocus();
}

If you set the default to either the "Yes" or the "No" button being checked by default, there will be no "Off" condition.