Sure so you will do something like this in your child theme functions.php file.
Download the Cairo font .ttf file and then add them to your child theme folder inside assets/fonts/cairo. Then replace the font file names with what you have downloaded below, for example replace below Cairo-Regular.ttf
with the actual name of the regular Cairo font.
add_filter( 'wc_cart_pdf_mpdf', function( $mpdf ) {
$mpdf->AddFontDirectory( get_stylesheet_directory() . '/assets/fonts/cairo' );
$mpdf->fontdata['cairo'] = [
'R' => 'Cairo-Regular.ttf', // Normal font weight
'I' => 'Cairo-Italic.ttf', // Italic font weight
'B' => 'Cairo-Bold.ttf', // Bold font weight
'BI' => 'Cairo-BoldIt.ttf' // Bold italic font weight
];
$mpdf->SetDefaultFont( 'cairo' );
$mpdf->AddFont( 'cairo' );
$mpdf->SetFont( 'cairo' );
$mpdf->autoLangToFont = false;
$mpdf->percentSubset = 100;
return $mpdf;
} );
You then might need to change the CSS font-family, so to do that copy the PDF CSS from the plugin folder wc-cart-pdf/templates/pdf-styles.php into your child theme folder child-theme/woocommerce/wc-cart-pdf/pdf-styles.php. Then in that copied pdf-styles.php in your child theme replace the body {}
font-family like this:
font-family: "cairo", sans-serif;
To add a unique code to each PDF that will take further custom programming, but I will see about adding this to the next release.