The plugin is fully translatable, you need a program like PoEdit to do it directly in your installation, or you can participate in the WordPress repository: https://translate.ww.wp.xz.cn/projects/wp-plugins/woocommerce-pdf-invoices/
Which is the language, that does not work for you?
So the words I will translate like:
Invoice
Invoice Date
Order Date
Order Number
Payment Method
Shipping Method
Will change, or I will need the premium version?
