Final answer:
A bank-issued document promising to pay the exporter once the agreed conditions are met is known as a Letter of Credit.
Step-by-step explanation:
The document issued by a bank that promises to pay the exporter upon receiving proof that the exporter has fulfilled all requirements specified in the document is called a Letter of Credit. A Letter of Credit is a financial tool used in international trade to provide an exporter with the assurance that they will be paid as long as they perform the services or deliver the goods according to the terms established in the credit. This method of payment is highly important in international trade due to the credit risk and the potential difficulty of legal enforcement across borders.