I believe you have an old version of Reader. For Reader X, launching PDF with Chinese Simplified characters will automatically redirect you to location where you can download Chinese Simplified fonts.
You can download Reader X from here http://get.adobe.com/reader/enterprise/
then try launching your pdf with fonts. Download fonts from the location you get redirected.
I hope this helps.
Assuming that you are looking for font packs for Windows:
Macintosh font packs can be found at http://www.adobe.com/support/downloads/product.jsp?product=10&platform=Macintosh