It is hard to keep the student list updated. One possible thing you can do to allow newly joined students to access your course before they are registered is to create a guest account. You then announce to your class the username and password of that guest account so that students who have not yet registered can access your WebCT course. Students interact with WebCT through a web browser. If your file has to be viewed using an application, say MS Word, you would need to create a hyperlink to that file in your WebCT course webpage .
Students can then use the application to view or print the file.
WebCT supports on-line assessment. You can control when students are allowed to take the quiz. However it is not advisable to conduct formal assessment on-line since it is impossible to control the environment in which the students complete the assessment. One exception is to require the students to complete the assessment task in a scheduled venue, say a computer lab under supervision. The course instructor can control whether to allow students to post anonymous messages in the bulletin board.