You cannot have a response set that is not editable by the user. However, you can use field scripting to create a template in which the user makes a selection, and then based on that selection, other fields on the template are populated. The user would not be able to edit these fields. You would need a field on the master pdf for the dropdown list where the user makes a selection and one for each of the fields that need to be populated based on that selection. The fields would be set up like this:
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