Sample code to alter the payment method text [https://wordpress.org/plugins/print-invoices-packing-slip-labels-for-woocommerce/]

functions.php

<?php// do not copy this line

add_filter('wf_pklist_alter_find_replace', 'wt_pklist_add_payment_method', 10, 6);
function wt_pklist_add_payment_method($find_replace, $template_type, $order, $box_packing, $order_package, $html)
{
	if($template_type=='invoice')
	{
		$paymethod_title=(WC()->version < '2.7.0') ? $order->payment_method_title : $order->get_payment_method_title();
		if(!empty($paymethod_title))
		{
			$find_replace['[wfte_product_table_payment_method]']=__($paymethod_title);
		}
		else
		{
			$find_replace['[wfte_product_table_payment_method]']='';
		}
	}
	return $find_replace;
}