Quotes and invoices are generated the moment you ask for them and are not stored in Whip Around. There is no document list, nothing added to the work order's Attachments, and no way to re-download an earlier export. The PDF lives on your device, like any other file you download.
If you need the document again, export it again — the figures will reflect the work order as it stands at that moment, so a document you send is always consistent with the work order behind it.
Because nothing is stored, a work order looks exactly the same whether it has been exported once, ten times, or never.