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