The Document Templates API combines Templates (MS Word documents) together with Objects (e.g. Job records) to produce documents in which the mergefields of the Template have been replaced with values from the Object. This is the system used internally by ServiceM8 to produce Quotes, Invoices etc for Jobs, but Addons can also use the Document Templates API to produce their own documents.
Refer to the Document Templates API Reference for details of the Document Templates endpoint.
Updated almost 5 years ago