public function setPaperFormat($paperFormat)
    {
        $defaultUnit = PHPRtfLite_Unit::getGlobalUnit();

        $paperWidth = PHPRtfLite_Paper_Format::getPaperWidthByPaperFormat($paperFormat);
        $this->_paperWidth = PHPRtfLite_Unit::convertTo($paperWidth, PHPRtfLite_Unit::UNIT_MM, $defaultUnit);

        $paperHeight = PHPRtfLite_Paper_Format::getPaperHeightByPaperFormat($paperFormat);
        $this->_paperHeight = PHPRtfLite_Unit::convertTo($paperHeight, PHPRtfLite_Unit::UNIT_MM, $defaultUnit);
    }