You can also email multiple invoices in QuickBooks Online. This helps you save more time by doing it by batch instead of one at a time.
Additionally, I've added an article that'll help you personalise and add specific info to your invoices. This ensures you'll be able to add the important details: Customise Sales Forms.
I suggest getting back to this thread if you need further assistance in managing your sales transactions. Just tag my name and I'll help you out.