Try these steps to prevent Word documents from automatically converting to a PDF:

1. Open the Word document that you want to prevent from converting to a PDF.
2. Go to the 'File' tab in Word.
3. Select Options from the drop-down menu.
4. Once the 'Word Options' window appears, go to the 'Save' tab.
5. Uncheck the box next to 'Allow automatic conversion to PDF'.
6. Click the 'Save' button in the 'Word Options' window.