1)Add Watermark to print page using HTML CSS 2) also using mpdf function into PHP controller at time of generate pdf add watermark

Add Watermark to print page using HTML CSS

// USING HTML & CSS
 <div class="watermark"> Watermark text ा</div>
 .watermark {display: inline;  position: fixed !important;  opacity: 0.25; font-size: 3em; width: 100%; text-align: center; z-index: 1000; top: 50%; right: 5px; writing-mode: horizontal-tb; }
 
// USING PHP and MPDF()

$mpdf = new mPDF('utf-8', 'A4-C');
$mpdf->showWatermarkImage = true;
// $mpdf->showWatermarkText = true;
// $mpdf->WriteHTML('<watermarktext content="watermark text alpha="0.3" />');
$mpdf->SetWatermarkImage(
imagepath, // image src path
0.10, // set opacity
array(90,120) // set image into page position
);
$mpdf->WriteHTML($html);