>In Europe there are several restrictions which in practice makes it illegal to use Word for invoicing. For instance there must be a system to make sure that each invoice number is unique and in sequence. Invoices must be impossible to changed after they are issued with normal software. Just to name a few.

I think nowadays even Word has the option to export as PDF, so if the .docx file doesn't even get saved, then that's it.

Still, I'd stay away from Office automation. Over the years whatever we did in it would get broken with the next version of Office, the options would be removed, and eventually it became a chore to explain to each customer that Office356 can't be automated.