Add mpdf in project

I beleave i need more information to help,

You should first load the plugin "config/bootstrap.php"
optinall edit “config/routes.php” for extension routing
Then configure in config/app.php or in controller

    Configure::write('CakePdf', [
        'engine' => 'CakePdf.WkHtmlToPdf',
        'margin' => [
            'bottom' => 15,
            'left' => 50,
            'right' => 30,
            'top' => 45
        ],
        'orientation' => 'landscape',
        'download' => true
    ]);

end than you can use the engine (mPDF) you set in your view