We are unable to wait. We found another plugin that works with the product add-ons:
https://www.ads-software.com/plugins/woocommerce-pdf-invoices-packing-slips/
Not being a wordpress developer – I’ll try to share my thoughts on this problem in the hopes that it might help the developer to fix the problem. Having dug into the code some, It seems to be a problem with using deprecated code to get the product information.
This might be the issue.
https://stackoverflow.com/questions/45032210/get-product-from-itemitem-deprecated-replacement-in-woocommerce
That code is used on line 85 of the print-content.php file. I have a suspicion that if that section of the code is changed to use the new calls, this problem will go away.
Hopefully that is helpful. I really like this plugin and hope you can get this working again!