At the moment you can either choose to have PDF invoices attached automatically or not, its a blanker choice. If this were an option on the client card to individually set them, it would work more efficiently due to many companies now requesting invoices sent as PDF. We don’t have this option chosen for all emails due to the fact, we use the history that can only be collected by the online link to help us when debt collecting to show proof of delivery , printing etc ( you can't say you didn’t get it if you print it..)
"Invoice PDF Choice in client card"