Dear Jessica,
Thanks for contacting Top China Travel!
It seems like you have never visited shanghai before. And we can arrange you to visit quite a few places here if you really want to utilize this stopover. Going to have a short visit to Shanghai downtown by your own might be a little bit tight, because maglev maglev train to downtown, but it stops at 21:40 and subway stops at 22:00. There are a lot of taxi, but taking taxi costs for nearly 400 RMB for round trip and even more.
Since there is 72 hours visa free rule in Shanghai so it is very convenient for you to have a short visiting in Shanghai. When you arrive Pudong, just leave the airport towards Arrivals. You'll need to fill in Arrival card. No visa required.
Any further request or question, please feel free to contact with us.