Can you send us the actual Report file (source code) and the PDF file, so that we can take a look "inside" and try to determine the cause for the problem. We will try to reproduce it over here. Another important question is what is the size of your PDF in megabytes?
Also, tell us the exact version of the Adobe Reader that you use to view the PDF. On our machines, with Adobe Reader 6.0 we see the Chinese text that you sent us perfectly by using the Arial Unicode MS Font.
I am attaching the report that we tested with. It is very simple and unbound -- only one TextBox with font Arial Unicode MS in the report header. You can give it a try on your machine and see what happens. Try all formats -- HTML, Image, PDF and tell us the results.