Check this out (Thanks Google) ...
WooCommerce PDF Invoices
It's automatic, attaches the invoices to Woo emails ... and best of all for all you cheapskates, lol ... it's FREE!
I don't need it in Australia, but I may use it anyway ... makes the transactions look more professional.
PS: If you paste
WooCommerce PDF Invoices into Plugins>Add New>Search ... you will see a few more options there too.
Simple Searching ... a lost art ... lol
I've yet to test this ... but like I said, there are other options there to try.