how to get PDF file from read stream end point

how to get PDF file from read stream end point

my webapp I create read stream endpoint url and use it in this custom function 

contDetails = zoho.crm.getRecordById("Contacts",contactId.toLong());
header_data = Map();
header_data.put("Content-Type","application/pdf");
file_object = invokeurl
[
url :"https://radiant-gorge-88984.herokuapp.com/pdf"
type :GET
headers: header_data
];
// response = zoho.crm.attachFile("Contacts",contactId,file_object);
info file_object;
return file_object;

and response looks like this 


 how can I get the response is pdf file? Thank you