1. If you right-click inside a data field that will give the option "Attributes" and allows the user to change just that fields font style/size.
2. If you right-click on an opened form (in the white area) outside of a data field you would get "Form Attributes" in the drop-down menu. That will change the font size throughout just that form.
Note: You will get a scary message:
Changing the master font for this forms affects every field in this form. In some fields, this MAY cause some entered data to be lost. Are you sure you wish to proceed with this change? “OK” or “Cancel”.
3. If the you go under Configure>Preferences>Data Fields tab and changes the "Font: Name/Size in Points" in that tab and clicks "OK" that will change the font size going forward for all forms. It will not change previously saved or forms open that are already filled out (use #2 above to perform that change).
Note: You can also change the added “User Field” by the methods outlined above in #1 and #3. In #3, go under Configure>Preferences>User Fields tab and change the "Font: Name/Size in Points" in that tab and click "OK". Also, uncheck “Snap to guides” and that will give you more freedom to move the user field around and position it exactly where you want it.