Older Windows versions like 7, 8 or 8.1 did not have a pre-installed default PDF viewer.
There might be some issues where troubleshooting steps can help to fix Microsoft Edge that Won't Open PDF Files. There are some particular errors that show up on the screen when the file is not openable. Microsoft Edge web browser has a default PDF viewer on Windows 10, but users face some issues still while trying to open the internet link or launching the particular file.
To repair damaged system, you have to purchase the licensed version of Reimage Reimage.