can I restrict a web user from filling out certain areas of the form (Office use only portion) and how
Unfortunately, you cannot restrict any particular user for from filling the form fields. However, you can create field conditions; which can hide a particular field (If the conditions are not met). Please visit the following link to know more about conditional form fields:- FormsCentral Help | Edit field properties (Please refer to- conditional form elements)
Note: Conditional elements are supported in web forms, but not PDF forms. To use conditional form elements, sign in to an Adobe FormsCentral account and move your form online.