public function addFootnote($noteText, PHPRtfLite_Font $font = null, PHPRtfLite_ParFormat $parFormat = null)
    {
        $footnote = new PHPRtfLite_Footnote($this->_rtf, $noteText, $font, $parFormat);
        $this->_elements[] = $footnote;
        return $footnote;
    }