Hi Gordon,
Great question!
This isn’t something that Event Tickets Plus directly facilitates, as it relies of one of WooCommerce or Easy Digital Downloads to handle monetary transactions and receipt generation.
To the best of my knowledge neither of those platforms directly support what you want, either (though they certainly send out order confirmation emails and receipts, they do not default to PDF or have special handling for donations that I’m aware of). That said, both have extensive ecosystems of plugins and extensions that may very well provide anything extra you need.
Does that help at all, or at least give you some further avenues to explore?