Bitlocker and Pre-Boot Authentication
When enabling Bitlocker on the Surface Pro, you'll find that it is impossible to set a PIN under the default configuration.
I can't believe I overlooked the GPO setting that lets you do this!
The GPO setting is as below:
Once you configure this, enabling Bitlocker will let you use a PIN for your Surface Pro!
Note: You must have your keyboard attached or a USB keyboard when you boot the system for this to work.