var path = "C:\\Temp\\"; 
var filename = "resolucion.pdf";

//reading file in binary code
var loadedFile = fs.read(path + filename);

//reading JSON file
var jsonInput = getvar("body");

//Sending the loaded file content using an HTTP POST request:

var url = "https://sandbox.esignlive.com/api/packages";

var Header = {
               "Authorization": "Basic (API KEY)",
               "Content-Type": 'multipart/form-data;boundary="separador"'
              };

var requestBody = "\n"

    + "--separador \n"

    + 'Content-Disposition: form-data; name="file"; filename="'+ filename+'"\n' 
    
    + "Content-Type: application/pdf\n"
    
    + "\n"

    + loadedFile + "\n"
    

    + "--separador \n"

    + 'Content-Disposition: form-data; name="payload"\n'

    + "\n"

    + jsonInput + "\n"
    
    + "--separador--\n";
    
var responseFromServer = http.post( url,  Header,  requestBody);

//console.log(responseFromServer.body.text);