It is very easy to add new footnotes. A footnote can be added directly from any post or page or defined globally from the footnotes admin menu. More info and additional WordPress plugins can be found at www.cminds.com.
The Fantastic Footnotes plugin for WordPress lets you easily add footnotes to your post or pages. Footnotes can then appear on the bottom of your article or anywhere else you may choose to display them. The plugin also supports showing an index page which includes all the footnotes and the related posts and pages in which they appear.