You can also copy this link, put your booking number in where ABC123 is and paste it in your browser and hit enter. Your invoice details will show with any OBC, shareholder credit, etc at the bottom of the document below Itemized Charges.
https://www.carnival.com/booked/document?BookingNumber=ABC123&IsPrintLuggageTagsSelected=true&IsPrintPassFlightSelected=false&IsPrintCruiseInfoSelected=true