FX_TRANSFER_4 conversion (payment_type AED_LOCAL_4, USD_LOCAL_4, EUR_LOCAL_4, GBP_LOCAL_4 or FX_TRANSFER_4) that has reached the partner and was not declined. The response body is the PDF itself (Content-Type: application/pdf, Content-Disposition: inline; filename="..."), not a JSON envelope. Read-only; no ledger impact.Confirmation letter not available for every other case — the id belongs to another client, is not a _4 transaction, has not reached the partner yet, was declined, or the partner has no letter for it (yet). Retry later when the resource is new.client/read scope. Owner-scoped.