code: public byte[] getDocument(String accountId, String envelopeId, String documentId) throws ApiException {
      return getDocument(accountId, envelopeId, documentId, null);
    }
docs: Gets a document from an envelope.
  Retrieves the specified document from the envelope. If the account has the Highlight Data Changes feature enabled, there is an option to request that any changes in the envelope be highlighted.  You can also use this method to retrieve a PDF containing the combined content of all documents and the certificate. If the account has the Highlight Data Changes feature enabled, there is an option to request that any changes in the envelope be highlighted.   To retrieve the combined content replace the &#x60;{documentId}&#x60; parameter in the endpoint with &#x60;combined&#x60;. /accounts/{accountId}/envelopes/{envelopeId}/documents/combined
  @param accountId The external account number (int) or account ID Guid. (required)
  @param envelopeId The envelopeId Guid of the envelope being accessed. (required)
  @param documentId The ID of the document being accessed. (required)
  @return byte[]