If you double-click a Standard Legal PDF or Word file and the Adobe Reader or Word program you want to use doesn’t launch, you need to change the settings on your device.
If the instructions below do not match exactly what you see on your screen, read your system’s FAQs or Help sections for the exact instructions to set a default program by file type.
On Windows 7 through 10, go to Control Panel > Programs > Default Programs > Set Associations (or some close variation to Set Associations).
Click on Associate a file type or protocol with a program. Now scroll down to the Protocols section, look for the .PDF or .doc or .docx row, then double-click on the filetype you want to change. Set the association you want to make for that program.
For laptops and desktops running macOS, open the Finder then locate a file of the type you want to set — PDF, .doc, etc.
With the file selected, open the File menu then choose Get info. Go down to Open with and choose your preferred app from the list. Once selected, click Change All and confirm your choice on the pop-up dialog.
If the Change All button is grayed out, it means the app you chose is already the default for files of this type; so no need to do anything else.