Stopping soft water at the shower head can be a cost-effective option, if the only concern is water in showers. Of course, to change the softness of the water for the house, different methods are necessary. Attaching a filter to a shower head is cheaper than installing a house-wide water-filtering system.
Measure the mineral content of the water to verify that it is too soft and determine by how much it will need to be hardened. Buy a filter that will fit in between the shower head and the pipe coming out of the wall. Be sure to attach one that is the right size. Be careful, as it is possible a plastic filter will be less durable than a metal fixture. Choose a size that suits the capacity you will need, depending on how often the shower is used.
The filter will reintroduce a small amount of a calcium-heavy mixture back into the water. This will adjust the pH and the "texture" of the water. It should feel different when taking a shower.
The quality of shower head filters varies widely. Use one that is adequately robust to tolerate rough use and also one that can be easily re-filled and adjusted to get the right amount of hardening effect.