SharpZipLib unzip with url

We are unzipping a .zip file using Server.MapFile(SomeZipFile), pulling out a .pdf and displying it in the webpage on our main website. 

byte [ pdfBytes;
if (r[1].ToString() != "")
{
  ZipFile f = new ZipFile(Server.MapPath("/PDMA/somezipdile.zip");
  ZipEntry ze = f.GetEntry(somepdf.pdf);
  BinaryReader br = new BinaryReader(f.GetInputStream(ze));
  pdfBytes = br.ReadBytes(256000);
  br.Close();
  f.Close();
}

The above code works on our webserver...

Now,  I'm creating a second wesite and I have to grab a .zip file from our sebsite and do the same thing, HOWEVER, i have to use http://www.ourwebsite.com/folder/PDMA/somezipdile.zip

open that file, find the PDF and open it.  This second website will be on a different server... Any help would be fantactic.

Thanks in advance,