In BPMN, should data objects appear at the source, destination or both?
CONSIDER: I sign a receipt for a pizza at the pizzeria and receive a copy of it. I take that receipt home and log it in Quicken. Does the data object representing the receipt most appropriately appear at the point I sign (create the object) or at the point where I log it into Quicken (finish with the object). Here's how I ~think~ it would work...
In significantly more complex documents, is it appropriate to have a duplicate instance of the receipt in each swimlane? What would the most appropriate notation be?
The usage of a data object just as shown in your diagram is correct.
Displaying Data Objects is kind of optional in BPMN. This means, you may decide to show important aspects, but need not display all data involved: just because you don't show a certain aspect, it doesn't mean it's not there. Furthermore you may show only the point of change (similar to create/update/delete) (by showing an associaton pointing to a data object) as well as only the point(s) of consumation (read) (by showing an association pointing from a data object).
In significantly more complex diagrams, I would recommend to only show the most crucial data aspects, because more than that is a significant problem for the overall readability. Unexperienced readers will mix up sequence flows and data associations, which really mean something very different. As a tendency, I would therefore also recommend to show only one side of the two mentioned (either creation/change or consumation) and would duplicate objects in favor of readability, but only IF they are really important enough to be shown at many places. In my mind, this is seldom the case.