This would be a perfect case for the Action Builder. What you can do is create a standard button called "Reset". Then from the Action Builder (Tools - Action Builder), create a new action with the condition of "when button (Reset) is clicked" and then the result change it to "set value of (object) with the object being the specific field that you want reset and the Condition to be "null". Then you can put all of the fields you wish to reset to 0 in this Action and then when the user clicks the button it will reset all of those fields back to null.
To create a Save button do the samething. Create a button called Save and then create a new action in the Action Builder. Saving a form is a built in result for a condition so all you need to do is select "Save the form" from the dropdown box in the result section.
The action builder is a great tool for making some extra functions in your PDF without the need to know Javascript or Formcalc. To be fair, it is more steps then just writing the code, but it is easier to understand the actions.
