Change to the Acrobat PDF viewer in Windows:
- Right-click on the thumbnail of any PDF file.
- On the menu, click Properties.
- A new dialog box will appear. In the first subsection, the text “Opens with:” indicates which PDF viewer is set as your default. Click the Change button.
- Select Adobe Acrobat DC or Reader from the list as your default.
- Click OK to save and apply changes.
Change to the Acrobat PDF viewer in Mac OS:
- Right-click on the thumbnail of any PDF file.
- On the menu, click Get Info.
- Navigate to the Open With: section and select Adobe Acrobat DC or Reader from the drop-down list.
- Tap Change All to apply this change to all future PDF documents. Tap Continue to finish.
Source: Adobe