Occasionally you may wish to change the default application in which a particular document opens. For example: you want PDF documents to open in Preview rather Acrobat or Word documents to open in Word 2011 vs. Word 2016.
For one-off changes, you can simply right click or press the control key and click on a document to get a pop-up menu to allow you to "open with" an alternate application.
To make change permanent, you'll need to take some extra steps:
Right click or press the control key down and click on the document type for which you'd like to change the default application. In this example, we'll change the default for opening Microsoft Word documents.
Choose "get info"
In the "get info" panel, click on the "open with" section and choose the new application that you'd like to be the default for that particular type of document. (Again, in this example, we're changing Word documents to open in Word 2011 vs. Word 2016.)
After selecting your desired new application, click the "change all" button. You'll receive a confirmation prompt asking if that's what you really want to do. Click continue, close the "get info" button and you're all set!