These instructions apply to Ubuntu 8.10 using Wine.
A. Plug in your USB to serial adapter.
B. Attach your serial pedal to the adapter.
1. Launch a terminal
2. cd .wine [Enter]
3. cd dosdevices [Enter]
4. ln -s /dev/ttyUSB0 com1 [Enter]
Launch Express Scribe.
Set your pedal as com1
Configure your pedal following the on-screen dialog. 
Enjoy!