There are a few different ways to get better Wi-Fi coverage throughout your home or office. A router should be able to cover at least 150 feet with Wi-Fi signal, but it could be less if there's a lot of interference from wiring in the walls or other devices. Simply moving the router to a new location could help.
Another thing to try is a Wi-Fi extender. Make sure that the extender is the same brand as your router so that it will be compatible. You can even use a second router in "bridge" mode to extend another router's signal.