public byte[] downloadDocument(PackageId packageId, String documentId) throws EslException {
   String path =
       template
           .urlFor(UrlTemplate.PDF_PATH)
           .replace("{packageId}", packageId.getId())
           .replace("{documentId}", documentId)
           .build();
   try {
     return client.getBytesAsOctetStream(path).getContents();
   } catch (RequestException e) {
     throw new EslServerException("Could not download the pdf document.", e);
   } catch (Exception e) {
     throw new EslException("Could not download the pdf document.", e);
   }
 }