You can download the invoices/receipts associated with your deposits by going to the Deposit Center.
From there, you'll scroll down to the Deposit History section to view your past deposits. There will be an invoice link and a receipt link that you can download associated with each deposit, and any deposits you make in the future will be displayed here with their respective invoice/receipt links as well.
Unfortunately, it's not possible to have invoices/receipts emailed directly to you when a payment is posted for your account. You do have the ability to set up additional email addresses, and have those email addresses receive email notifications when a deposit takes place. However, if you want to actually view/download invoices and receipts associated with these deposits you'll need to do so within the Merchant UI.
You can set up additional email addresses, if necessary, by going to the Account Details page (under Account Information).