1. Go to the Mac’s Finder.
2. Find the PDF file type you’d like to open with a specific app, and select it.
3. Click on the File menu and select Get Info.
4. Expand Open with: by clicking on the triangle to the left.
5. Select the Open with: menu, then choose Foxit PDF Reader to open all documents like that one.
6. Click the Change All… button.
7. You’ll get a dialogue box asking you to confirm your choice. Click Continue. (Figure 1)
8. Close the Get Info window.

Figure 1: Dialog Box

Use any of the options below to set Foxit PDF Reader as the default in Windows.

Change the Default App in your settings

• Click on the Start menu. It’s the Windows logo in the bottom left of your screen.
• Click on Settings.
• Click on System.
• Click on Default apps.
• Click Foxit PDF Reader to open all PDF documents.

Use the command under the Help menu tab

• Open the Foxit App, go to Help, then select Set to Default PDF Reader.

Use the options in Preferences

• Open Foxit App, go to File > Preferences > File Associations > Advanced > check all options > click on OK > click on Make Default PDF viewer > click on OK to apply the change. 

Use the Open With in File Explorer

• You can also right-click a PDF > choose Open With > select "Choose another app" > select the Foxit app > check the option "Always use this app to open .pdf file" > click OK to apply the change. 

Use the File association in Settings or Control Panel

• Refer to this article for specific steps.