When you open a file, EditPad looks at the file's extension to see which type of file it is. If you open a file with an extension not associated with any file type in EditPad's file type configuration, you can change the file type through Options|File Type.
Changing the file type will cause EditPad to change the file's settings for auto indent, line numbering, word wrap, etc. to those specified in the file type configuration for that file type. It will not change the file's extension. Use File|Rename and Move to change the file's name and extension.
Configure File Types