The only way I know to make any kind of a cane plant shorter is to cut it back to about 2 or 3 inches above the soil level. Don't throw away the old rootstock, just leave it in its pot and continue to care for it, and eventually it will resprout new branches and leaves.
You can trim the stem of the leafy part to the length you want it to be, and plant it in a moist, well-draining medium. It will sprout new roots and continue to grow.
If you have a section of bare cane left over, you can cut it into sections 4 to 5 inches long and start a brand new plant from each section.
If you decide to try propagation to get your plant back within the bounds of its space, you can plant a few plants in one pot, using plants of different heights. The shorter ones will hide the bare stems of the taller ones, and you'll have a very full-looking specimen plant.
That's the only way I know of to shorten a dracaena that has grown too tall for it's location. Other members may have other suggestions, though.
