$config=[

        'mode'=>'utf-8',
            'useAdobeCJK'=>true,
            'autoScriptToLang'=>true,
            'autoLangToFont'=>true,
            'useSubstitutions'=>true,

            'format' => 'A5',
            'orientation'=>'L',
            'margin_top' => 3,
            'margin_left' => 5,
            'margin_right' => 5,
            'margin_bottom' => 0
]
  $mpdf = new Mpdf($config);
        $mpdf->WriteHTML($content);
   $mpdf->Output($filename,$dest);

设置字体 字体不起作用请调整以下参数

'useAdobeCJK'=>true,
'autoScriptToLang'=>false,
'autoLangToFont'=>false,