Another option would be to define your own "Note" attribute, create a form that contains that attribute, and assign the attribute to the Form attribute of the Document (or derived) template item. Then your custom attribute will be displayed above the document in the detail area for editing.
http://www.kinook.com/UltraRecall/Manual/formviewer.htm
http://www.kinook.com/UltraRecall/Manual/form.htm