Pforzheim is over twenty-five kilometers from Karlsruhe, but is still integrated into the Karlsruhe "S-Bahn" light rail system.
The trains in this system are like large trams that run on the streetcar tracks in Karlsruhe, but then switch to normal railroad tracks to go further out into the countryside. In Pforzheim they stop inside the main station just like any other trains.
From Pforzheim you could take one of these "tram-trains" northwest to Karlsruhe, east to Bietigheim-Bissingen or south to Bad Wildbad, in the Black Forest.
Regional Express (RE), InterRegio Express (IRE) and InterCity (IC) trains run once or twice an hour in each direction between Karlsruhe and Stuttgart, all calling at Pforzheim.
The timings are only slightly different: 18 minutes from Karlsruhe to Pforzheim on the IC, 20 minutes on the IRE and 23 on the RE.
Second and third photos: On the Regional Express to Pforzheim.
You do see people cycling in Pforzheim, but the infrastructure in the city center is rudimentary at best.
There is absolutely no place to rent a bicycle in Pforzheim. The woman at the tourist information made some phone calls for me, but came up with nothing.
Second photo: On the plus side, Pforzheim is connected to some nice regional cycling routes. Here the signs point to Vaihingen and Bad Wildbad, among other places.