You can remove the adware yourself in many cases. To do it, go to Windows' Programs and Features (you can type this section name right into the search bar,) choose the adware program from the list, and press Uninstall. If you are dealing with a browser plug-in, you can remove it from your browser's settings. The path varies throughout browsers, but it is roughly such: Main Menu -Settings - Extensions. Select the troublesome extension and press Remove. However, the pest often takes self-preservation measures. It can freeze the browser as you open its settings so that you don't delete an annoying extension easily. Moreover, if adware comes as a stand-alone program, it may not always be clear about its title. So you have to be sure which program exactly you wish to delete. Finally, you might run onto sneaky adware. In such a case, you will need to detect a foreign process, remove an executable file responsible for it, and you will also have to check for an automatic downloader that might still be present on your machine. The latter will download the adware again, no matter how many times you wipe it out. For such cases, an antivirus program is the best solution.
As for the safety of such procedures, the only harm you can do is accidentally remove a benign program. Also, some downloaded applications may cease working after you delete their adware component.