// Stream PDF kit to client
Byte buffer = File.ReadAllBytes(filePath);
base.Response.ContentType = "application/pdf";
int length = buffer.Length;
base.Response.OutputStream.Write(buffer, 0, buffer.Length);
But I saw this exception message:
Sys.WebForms.PageRequestManagerParserErrorException: The message received from the server could not be parsed ...
It turned out that I should using Response.Redirect() to another page to show the PDF file in browser. To avoid the same exception, there is no AJAX code in the second page.