When invoice send by PDF how do you mark as sent without sending again?

Thanks for joining us here on the Community, jolabucks-icloud 

Currently, there is no way to mark the invoice as sent without emailing this from the system, as a workaround you can send the invoice to your own email so that this updates to show as sent.

We're always looking to adapt and improve in-line with customers needs so we'll be sure to pass this on as feedback on our end. 🙂