It's up to you. As far as I know, all stm32f103 I/O have built-in pull-up and pull-down, which can be switched on or off as you see fit. If you prefer, you can program them to be digital outputs (high or low), or set them as analog inputs (which disables the digital input circuit).
What you should avoid is having any of the pins programmed to be digital inputs but floating, as that will cause class-A current flowing in the input transistors (increasing the overall power consumption with no benefit).
Probably most useful is pulled-up or pulled-down, so you can later choose to use the pin as a debugging input or output.
Hope this helps,
Danish
