Links. No stage of a sale is an island. An order's page offers its waybills and its invoices; a waybill offers the invoice that charges for it; an invoice offers the receipt that settles it. Each link creates the next document with everything already known carried across — customer, lines, prices, the frozen rate — and each appears only when you hold the permission to create that next document (1.5). The customer's 360° page (§3.6) gathers the whole chain per customer.
Prints. The order prints as the customer's confirmation; the waybill prints as the delivery note that travels with the goods; the invoice, credit note and receipt print as the formal documents of record; the statement prints (or sends) as the customer's own summary. Your print preferences — tax breakdown, signature blocks, totals in words, footer text (0.6) — shape all of them.
Documents. Every print files itself automatically into the document library under your company's file plan, attached to the record it came from (Chapter 14) — the invoice PDF lives with the invoice, the delivery note with the waybill — so the paper trail is reconstructable from either end. Files you attach by hand inherit the record's visibility: whoever may see the customer sees the customer's attachments.