Some of our donors expect invoices that can be downloaded for their record-keeping and to share between departments for approval. I think it would be beneficial to include a PDF version of the invoice in the email when the option "Email this invoice to your contact" is selected. Additionally, I think it could be helpful to add a "Print Invoice" button to the page that opens when the donor clicks the link in the email. More technical donors may understand that they can just print the page for their records, but others may not.