submitForm doesn't submit the whole pdf content to server side

I found that it's strange after I submitted the pdf file with keywords to server side, then I found the pdf content on server side lost the keyword content.

that's simple to make the things happen again.
ctrl+d, set some keywords into keywords field of any document,
ctrl+j raise up the console, input:
this.submitForm(
{cURL: "http://test08/test/echofile.aspx",
cSubmitAs: "PDF"
});

where echoFile.aspx just return the PDF file back;
ctrl+d, and then you found no keywords there.
Also, the other info's will lost too like the property: this.info["staffID"] = '1990213';

---------------echoFile.aspx as below-----------------
<%@ Page Language="C#" debug="true" %>
<%@ import Namespace="System.IO" %>
<% int len = (int)(Request.InputStream.Length);
byte[] bytes = new byte[len];
Stream stream = Request.InputStream;
stream.Read(bytes, 0, len);
Response.ContentType = Request.ContentType;
Response.OutputStream.Write(bytes, 0, len);
Response.End();
%>
----------------------------------------------------------------

* Testing under Acrobat 8.0
any one could help?

thanks,
Kendrew.