How to to convert string response to ArrayBuffer?

From server I am getting the pdf response as string format, Now on client side, I want to convert it into ArrayBuffer, So that we can change again in pdf.

I am converting it into pdf, like following, but is not pdf is getting corrupted.

function str2ab(str) {
          var buf = new ArrayBuffer(str.length*2); // 2 bytes for each char
          var bufView = new Uint8Array(buf);
          for (var i=0, strLen=str.length; i < strLen; i++) {
            bufView[i] = str.charCodeAt(i);
          }
          return buf;
    }

Above function I got from stackover flow, I change Uint16Array to Uint8Array, pdfkit uses utf-8 uncode formate..

service.getAddress(reqData).then(function(response){
                if(response.data.error ===1){
                    toastr.error(response.data.message ,"Unsuccessful");
                }else{



                    var uintStr = str2ab(response.data);
                    var file = new Blob([uintStr], {
                        type : 'application/pdf'
                    });
                    //trick to download store a file having its URL
                    var fileURL = URL.createObjectURL(file);
                    var a         = document.createElement('a');
                    a.href        = fileURL;
                    a.target      = '_blank';
                    a.download    = envelopeObj.customer_name+'_'+ 'envId_'+envelopeObj.envelope_id+'.pdf';
                    document.body.appendChild(a);
                    a.click();
                }
            });

To using pdf kit to convert it into string format.

add_str = render_to_string(address_template_path , {"address_dict": address_dict})
pdfkit.from_string(add_str, file_location)

address_pdf = open(file_location)
response = HttpResponse(address_pdf.read(), content_type='application/pdf')  # Generates the response as pdf response.
response['Content-Disposition'] = 'inline;filename= %s' % envelope_id