API and donwloading pdf attachement from postUrl response

Hi any one knows if this is possible... I'im trying to to see if its possible to use an external service/site.

to send and fill PDF with zoho data and download the API attachement responses after pressing a custom button.

all i have manage to do is get the filename of the attachement from the API

By the way i am not a programmer by any means... just trying to figure this out..

My Custom function is..

headerMap = Map();

headerMap.put("Accept-Language","en_US");

headerMap.put("Accept","application/json");

headerMap.put("Authorization","Basic " + "***username***");

requestMap = Map();

requestMap.put("data[Produit_4]","test");

filename = response.getJSON("responseText");

openUrl(response,"open window");

return filename;

The full response to this is porstUrl is....

{"responseText":"89da9436-c479-46ec-84be-8dd838bd208a.pdf","responseCode":200}