Yes – Audacity is free recording and editing software ideal for voice-overs and singers.
You can enhance your voice using the Effects option, which is located in the toolbar. For example if you want to boost the presence and fullness of your voice go to Effects -> Compressor. Use the default setting to begin with and see if it is enough for your voice.
You can also adjust equalisation (EQ) which means adding more/less bass, mid-tone and treble.
A powerful, free tool.