You already learned about Document Types in Chapter 11, so setting up the To Do document type should be old hat:
In Project Builder, select the default document type in the Document
Types listing. Change its name to
Leave the role set to Editor.
Make the document extension
In Section 14.1.2, you learned that application
signatures can be associated with a document to create a “strongly
bound document.” You can add the To Do application signature to the To
Do document type now if you wish; simply type
ToDo in the OS types list. If you don’t want to
create a strongly bound application, leave this blank (delete the
To associate an icon with this document type, follow the same procedure you used in the previous section to create an application icon, and then specify the name of the document icon file.