Invoices feature is available in Sales Pack extension. Invoice record represents a group of products or services with their quantities and prices.
Invoice can be created from existing Opportunity, Quote or Sales Order.
Printing to PDF
Invoices can be printed to PDF. You are able to create multiple custom templates, which include your custom fields and fit your company design.
Sending in Email
Invoice PDF can be send in email as an attachment. On the detail view, click dropdown next to Edit button and then click Email PDF.
For more detail information about using Invoices see documentation.