Sample function to include form custom field data in GiveWP PDF Receipts

givewp_pdf_cutom_tags.php

<?php
function givewp_pdf_cutom_tags( $template_content, $args ) {
	//$donor_info    = give_get_payment_meta_user_info( $args['donation_id'] );
	$post = get_post($args['donation_id']);
	
	if ($post->post_parent) {
		$post_id = $post->post_parent;
	} else {
		$post_id = $args['donation_id'];
	}
	$codice_fiscale = get_post_meta($post_id, 'meta_donation_codice_fiscale', true);
    
	$template_content = str_replace( '{meta_donation_codice_fiscale}', $codice_fiscale, $template_content );
	return $template_content;
}

add_filter( 'give_pdf_compiled_template_content', 'givewp_pdf_cutom_tags', 900, 2 );