I am going to plot for instance:
Plot[Evaluate[
PDF[ExponentialDistribution[#]][x] & /@ {1/2, 1/5, 1/25,
1/1000}], {x, 0, 50}, AxesOrigin -> {0, 0}]
Now, when someone prints this black and white, I would want him to be able to distinguish between the curves (a line, then a dotted line and so on). How would you suggest me to change the code, to achieve this goal?