protected function setDefaultMargins($margins)
    {
        if (!is_array($margins)) {
            $margins = array($margins, $margins, $margins, $margins);
        }

        if (!isset($margins[2])) {
            $margins[2] = $margins[0];
        }
        if (!isset($margins[3])) {
            $margins[3] = 8;
        }

        $this->_defaultLeft   = $this->cssConverter->convertToMM($margins[0].'mm');
        $this->_defaultTop    = $this->cssConverter->convertToMM($margins[1].'mm');
        $this->_defaultRight  = $this->cssConverter->convertToMM($margins[2].'mm');
        $this->_defaultBottom = $this->cssConverter->convertToMM($margins[3].'mm');
    }