If you would like to delete (remove) a mapped field from your Document, you need to use the 'Delete Field' function in Reporting
To delete a field, you will need to make sure you have versioned your Document and are in 'draft'; and then in Edit mode:
When in Edit mode, you will be able to use the Reporting functionality. To delete a field, you need to find the relevant field on the Document, and select it by ensuring that your cursor is on the field.
You can find the field either by scrolling through the Document; or using the Field Navigation functionality to 'select' your field. Its only when you have clicked on a mapped field that the Delete Field function will be enabled:
When you have selected the field you want to remove, click Delete Field and it will be removed.
You will need to SAVE your draft for the changes to be Saved.