In the Open and Import dialog boxes, certain extensions are suggested by default for each document type you select in "Files of type." You can add to or remove some extensions for each document type.
To define the default open extensions:
1. Choose Preference ® Options,
File.
In the Input category of the File Preferences dialog box:
2. Add to or delete any of the Extensions, using the asterisk (*) as a wildcard character. Leave a space between each extension.
Tips
3. Click Save. Click OK.
The selected extensions are used for the next documents you open.