I am traveling to the Shanghai World Expo Pavilion for a trade show

Do you mean the Shanghai World Expo 2010 venue or Shanghai New Internation Expo Centre? If it is the venue of Shanghai World Expo 2010, you can take subway line 2 from the airport to the Century Avenue, then transfer to subway line 4 and get off at Nanpu Bridge. You can then walk to the expo site.
If it is the Shanghai New International Expo Center, you can take the Maglev train to Longyang Road and then catch a taxi there.