In the current version the Customer Orders list itself has no export button (its DataTable is configured with an empty buttons list). To get a document for a single order use Print Order on the order page (an icon-and-text button in Quick Actions), which produces a PDF invoice via Snappy/wkhtmltopdf and falls back to a clean print-ready page if that isn't available. For order-level exports use the Reports section, which does have PDF/Excel buttons on its reports.