I have a client requesting that when they print an invoice that includes billable expenses, the receipt uploaded on that expense line be printed as well? Any thoughts? I have not found a way to do this.

I would expect you'll have to build an xml to pdf process to accomplish this where you insert your images at the end of the document.

you may be right but I hope not

you might try #C466X49JB

The expense receipt image is not in the invoice data and it doesn't look like you can create a custom line field and source it from the expense report. Therefore you won't be able to do this with the regular AdvancedPDF method and you're going to need a script, that will get the invoice data, add the file id of the receipt image to the data set, and combine this with a freemarker template (like advanced PDF) to generate the invoice with expense receipt images.