Yes, you can download the invoice from Zoho FSM, send it to your customer, and then mark it as sent in Zoho FSM.
Downloading an Invoice in Zoho FSM
- Open the invoice.
- From the Send Invoice dropdown, select Download.

The invoice will be downloaded in PDF.
Marking an Invoice Sent in Zoho FSM
- Open the invoice.
- From the Send Invoice dropdown, click Mark as Sent.

This option is available only when the invoice is in the Draft state.