To change the default application follow the steps below.
1. Click on the Start menu.
2. Click on the settings tab.
3. A settings window will pop up. In that window select the Apps option.
4. This will open an Apps and features window. On the left hand side of the window there is an apps menu. Select the Default apps tab.
5. If the default application you are trying to change is in the quick access menu. Selecting an application will populate a menu of options. Selecting any of the choices in the menu will change the default application to that choice.
6. If the default application you are trying to change is NOT in the quick access menu. Scroll to the bottom of the quick access menu, you are presented with secondary options to change your default applications (changing your default .pdf viewer would be done this way). Select Choose default apps by file type. After selecting Choose default apps by file type, a window titled "Choose default apps by file type" gets displayed. On the left hand side of this page are a list of file extensions. To the right of the file extension is that extension's default application. Clicking on the application populates a menu with replacement options. Selecting an option with replace that extensions default application.