During the install, Office prompts you to perform a "typical" installation vs. a "custom" installation. If you select "custom", you can pick and choose which components to install.
Once installed, you can go to "Programs and Features" as if you wanted to uninstall the program but when you highlight Office, select "Change" instead of uninstall. You will then be able to pick and choose which components to remove from, or add to, the existing installation.