I was studying PCB design in a college.
It is not as simple as u think.
You need to study not only the software, such as Mentor Graphics' Design Capture and PCB Expedited, or Orcad.
Then you also need to learn about some rules when you design, for example how to get a clean signal (where to put the capacitors, when to put the ground plate).
If you really are into this, then you should go to college and take a program, not just a course.
The life of PCB designer is not exciting. It is repeating everyday. But as a hobby, you can get some fun out of it.
The hard part is to find someone who will do the PCB manufacturing for a small quantity.