The 'New Invoice' button creates an empty (ad hoc) Invoice (with out any data as far as billings added yet) which allows you to add 'line items' (from the detail page) to charge for services rendered or expenses incurred- that may have not been created as billings yet. Once you have added the line items then you can click print from the invoice detail page and create the finished Invoice.
Navigate to the Invoices Tab
Click the 'New Invoice' Button
Set the Invoice Details
Returned to the New Invoice's Detail Page
Add Line Items
See: Adding Line Items to your Invoice
Generate the New Invoice PDF
Click the Print Button
Pdf Generation Confirmation Pop-up
Click OK
Notes & Attachments
Navigate to the Notes and Attachments section of the Invoice detail page and click View
Invoice PDF
