Want to go back to pdf reader in MacOS

I'm using Adobe Acrobat Reader DC version 19.021.20056 on my MacBook Pro (Retina, 15-inch, Mid 2015) running MacOS 10.15.1. I chose to switch to Acrobat to be able to see some documents created, supposedly, in another Adobe application...which one I don't know, but it worked. Now I would like to go back to using the pdf reader function in the MacOS. How do I disengage the Acrobat Reader?