code: public byte[] getDocument(String accountId, String templateId, String documentId) throws ApiException {
      return getDocument(accountId, templateId, documentId, null);
    }
docs: Gets PDF documents from a template.
  Retrieves one or more PDF documents from the specified template.  You can specify the ID of the document to retrieve or can specify &#x60;combined&#x60; to retrieve all documents in the template as one pdf.
  @param accountId The external account number (int) or account ID Guid. (required)
  @param templateId The ID of the template being accessed. (required)
  @param documentId The ID of the document being accessed. (required)
  @return byte[]