All your PDF files open in Adobe Reader, but you want them to open in Preview. All your JPEG files open in Preview when you’d rather they open in Photoshop. How do you change what Mac OS X uses as the default application for particular file types? We’ll show you how, in four steps.
Find a file that’s the type you want to change. In this example, we want to set Photoshop to open any time a JPEG file is double-clicked.
Right click on your file, and then select Get Info (or click on the file once, then go to File -> Get Info, or select the file and press Command-I on your keyboard). This will open the Get Info window.
In the Get Info window, the Open With pane displays a pull-down menu with the application that is currently set to open the file. Click on that pull-down menu, and a pop-up list will display all the applications on your Mac that are able to open the file.
Move your mouse down the list and click on the application you want to open your file (in our example, we select Adobe Photoshop).
Now that you’ve changed the default program for this file, the button for Change All is active. This button will set your Mac to use the selected application to open files of this type. Click on that button.
On the dialog window that pops up asking if you are sure, click Continue.
Done. You can close the Get Info window. If you want to change the default application again or change it back to the previous application, just go through these steps again.