Right click on the file you desire to open in Adobe - > Hover over “Open with” and select “Choose default program”.
The “Open with” dialog will appear.
If “Adobe Acrobat Reader” is in the Recommended Programs section, click on it.
If it’s not in the Recommended Programs section, click on the “Other Programs” down arrow circled in Red and search for Adobe:
Make sure the “Always use the selected program to open this kind of file” checkbox is checked.