Controlling the files you create (or are directed to modify) means that others will not have access to copy your work. In other words, don't share your files.
Students have said that they shared the file so they the other student could see how the completed assignment should look. Don't try this excuse because professors don't buy it. Here is the problem: When you share the file you share your typing efforts (or your original work and your efforts to create that original work). Back to our pancake example: "I only gave the other student a plate of completed pancakes, so he could see what the end product should be." All the other student does is add some blue berries and whip cream. If a student makes minor modifications to your work (changes the spots where his name is at) and turns it in as his work you will be included in the charge of academic dishonesty. Unless specifically authorized by your professor, don't share any files that you create or modify with another student -ever, not now and not in the future.
Here are two suggestions for controlling access to your files:
When using a course delivery software product or learning system, such as Blackboard Vista, don't give another person your password. With the password, they will have access to your submitted assignments including the files that you created.
Don't leave your files on a machine where others may have access to them. If multiple students are using or have access to the same machine (often happens with students living in the same household husband/wife, siblings or roommates) or in an on-campus course where many students will have access to the machine store your files on a flash drive. Physicially control who gets access to your flash drive