Yes you are correct, us RFIC designers are constantly getting PCBs made with differring characteristic impedance (often 50ohm, but not always necessary) tracks to match the impedance we are teminating in (and therefore not introduce rotation on a smith chart). We do this by altering the track width depending on the other parameters of the PCB (er, dielectric thickness, conductor dimension etc.)

There are quite a few tools out there for designing microstrips (single track on top layer of PCB) or stripline (embedded track).

As I don't design PCBs (i only check that the PCBs made meet my criteria) i often use the lmg program included in cadence.

But i'm sure if you do a google for you'll find some good stuff or try
http://www.circuitsage.com/tline.html

hope this helps