how to open pdf on button click event

Hi All,
I need to open a pdf document with Save/Open Dialog when a button is clicked.
I am doing something like below
Response.ContentType = "application/pdf"
Response.AppendHeader("Content-Disposition", "attachment; filename=Test.pdf")
Response.TransmitFile(Server.MapPath("Test.pdf"))
Response.End()
I get the following errorin my error log file
System.Threading.ThreadAbortException Thread was being aborted. Stack:    at System.Threading.Thread.AbortInternal()
   at System.Threading.Thread.Abort(Object stateInfo)
   at System.Web.HttpResponse.End()
and the following error on my page
Sys.Webforms.PageRequestManagerParserErrorException:The message received from the server could not be parsed. Common causes for this error are when the response is modified by calls to Response.Write(), response filters, http modules, or server trace is enabled.< ...