Below you find a short description how you can change the default program for opening PDF files in Windows and macOS.

Windows

Change the Default by Using 'Open With' in File Explorer

Instructions	Images
Open File Explorer and navigate to a folder containing a PDF file. Right-click on a file and choose “Open with > Choose another app”
A pop-up will appear that will let you choose a program for just one time. Or you can also select the “Always use this app” link to make it permanent. From this window, choose the default PDF reader of your choice. In this example we choose Firefox as our PDF reader utility.

Instructions	Images
Open the document you want to convert, and then click the “File” tab.
On the backstage screen, select “Save As” from the list on the left.
On the Save As screen, select where you would like the PDF to be saved. Next, click the dropdown arrow on the right side of the “Save as type” box, and select “PDF (.pdf)” from the dropdown menu. If you want, you can change the filename right here. When you’re finished, click the “Save*” button. After saving the PDF, you’ll be returned to the Word document, a new PDF will open automatically in the default PDF viewer.