It's actually very easy to switch the default PDF readers. Windows doesn't have this option in the Settings menu, but you can use the standard file association to assign a default application for the PDF file format.
Simply locate a PDF file and right click it. Choose Open With > Choose another app. From the list, select openPDF Editor and tick the Always use this app to open .pdf files and that's it. Afterward, double-click the PDF file and openPDF Editor will open.