Even after having an Adobe alternative on your Mac, if you want Adobe Acrobat as your default PDF reader, here are the steps to do so -
1. Hold the Control key and then single-click a PDF file
2. Select Get Info
3. Click on the Open with dropdown
4. Choose Adobe Acrobat
5. Next, click on the Change All button
There you are! Adobe Acrobat is now your default program for your PDF documents.