Select Edit > Preferences
and select File Types/Editors from the Category list.
Filename extensions, such as .gif, .wav,
and .mpg, are listed on the left under Extensions. Associated editors
for a selected extension are listed on the right under Editors.
Select the file type extension in the Extensions list
and do one of the following:
To associate a new editor with the file
type, click the Plus (+) button above the Editors list and complete
the dialog box that appears.
For example, select the application
icon for Acrobat to associate it with the file type.
To make an editor the primary editor for a file
type (that is, the editor that opens when you double-click the file
type in the Files panel), select the editor in the Editors list
and click Make Primary.
To dissociate an editor from a file type, select
the editor in the Editors list and click the Minus (-) button above
the Editors list.
Click
the Plus (+) button above the Extensions list and enter a file type extension
(including the period at the beginning of the extension) or several related
extensions separated by spaces.
For example, you might enter .xml .xsl if
you wanted to associate them with an XML editor installed on your
system.
Select an editor for the file type by clicking the Plus
(+) button above the Editors list and completing the dialog box
that appears.