How can I reduce the number of microprocessor pins I need to use?
Let the user select the options by binary code using three input pins.
Table 1. Jumper options.
Option   J0   J1   J2
  0      0    0    0
  1      1    0    0
  2      0    1    0
  3      1    1    0
  4      0    0    1
  5      1    0    1

And you still have more if you ever need them.
Other options include using an analog input.



simulate this circuit &ndash; Schematic created using CircuitLab
Figure 1. A solution using only one analog input.
Note that this solution gives the user the option to short-circuit the supply by inserting J1 and J5. You may wish to add an R5 into the ground wire to limit the current in this case.