Summarize this article:

An easy way to do this is to press ⊞ Win+E.  A context menu will appear. Another menu will expand. Even if you have Acrobat Reader showing as one of the option, you should still select this option.  ” Adobe Acrobat Reader is now your PDF default viewer.

Summary:
Open the Windows File Explorer. Open the folder that contains a PDF file. Right-click the PDF. Click Open with. Click Choose another app. Select Adobe Acrobat Reader DC. Check the box next to “Always use this app to open .pdf files. Click OK.