Como converter de string para pdf?

Atualmente, estou usando o serviço Restful no asp.net c # e o seguinte é opdf string que recebo, gostaria de convertê-lo e salvá-lo como updf Arquivo. Como devo fazer isso?

static string HttpGet(string url)
        {
            HttpWebRequest req = WebRequest.Create(url)
                                 as HttpWebRequest;
            string result = null;
            using (HttpWebResponse resp = req.GetResponse()
                                          as HttpWebResponse)
            {


                StreamReader reader =
                    new StreamReader(resp.GetResponseStream());
                result = reader.ReadToEnd();
            }
            return result;
        }

/****************************** result returned ******************************/ 
%PDF-1.3
%����
3 0 obj
<<
/Linearized 1
/O 5
/H [ 526 186 ]
/L 47163
/E 46840
/N 1
/T 47053
>>
endobj                          
xref
3 11
0000000016 00000 n
0000000436 00000 n
0000000712 00000 n
0000000957 00000 n
0000001056 00000 n
0000001078 00000 n
0000046475 00000 n
0000046502 00000 n
0000046611 00000 n
0000046725 00000 n
0000000526 00000 n
trailer
<<
/Size 14
/Info 1 0 R
/Root 4 0 R
/Prev 47044
>>
startxref
0
%%EOF
4 0 obj
<<
/Type /Catalog
/Pages 2 0 R
>>
endobj

13 0 obj
<<
/Length 104
/P 0
/S 46
>>                   
stream

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