403 error when opening PDF with chrome pdf viewer -

we host c# 3.5 net web app in iss 7.5.

pdf files generated , put in directory. listing of directory disabled. browsers (ie10, ff, opera...) can access pdf.

when accessing url chrome, pdf loaded... 403 error. if disable chrome internal pdf viewer , tell use adobe's, works fine.

what can wrong?

problem explained here: http://productforums.google.com/forum/#!topic/chrome/1msjcjabwpe

but mentioned kb cannot applied we'll httphandler.

    public void processrequest(httpcontext context)     {         switch (context.request.httpmethod)         {             case "get":                  if (!context.user.identity.isauthenticated)                 {                     formsauthentication.redirecttologinpage();                     return;                 }                   string requestedfile = context.server.mappath(context.request.filepath);                  context.response.contenttype = "application/pdf";                 context.response.transmitfile(context.server.mappath(context.request.filepath));                 context.response.end();                  break;         }     }