You can view, download and print all invoices in the transaction history area of the Billing page.
First, go to Management at the top of your screen and then select Billing from the left. Once on the Billing page scroll down to Transaction History.
To make it easier to sort through your invoices for printing select Card Charges Only at the top right of the Transaction History section. where it says Show All Transactions

Click View next to the invoice you want to select.

This will open a new tab and from there you can click on the Print Invoice button at the top right of the screen to open a print dialog box where you can either print or download the invoice.

Invoices can be printed/downloaded as many times as you need.
Please see Billing Management and Payment Settings for more information on Billing