What code can I use to trigger a print-out from a PHP context?

The code fragment below should work:

<?php
global $woocommerce_simba_printorders_printnode;
$woocommerce_simba_printorders_printnode->woocommerce_print_order_go($order_id);

This will print using your default settings.

Posted in: WooCommerce Automatic Order Printing (PrintNode)