Coupons used in invoice?

In the free version you can add the used coupons with a small code snippet:

//Add used coupons to PDFs
add_action( 'wpo_wcpdf_after_order_details', 'wpo_wcpdf_coupons_used', 10, 2 );
function wpo_wcpdf_coupons_used ($template_type, $order) {
	if( $used_coupons = $order->get_used_coupons() ) {
		$coupons_list = implode(', ', $used_coupons);
		echo '<h4>' . __('Coupons used') . '</h4>';
		echo '<p>' . $coupons_list . '</p>';
	}
}

If you haven’t worked with code snippets or functions.php please read this: How to use filters

With our Premium Templates you can do this without any coding, either by placing the {{used_coupons}}:

or by enabling it for the discount row in the totals:

Thank you very much for your help! I’ll try out the function you’ve provided, many thanks.