This task can be done by using Manage Categories. It’s sounds a bit tricky, but it’s simple.
Create a new category under the area you wish the files to be stored, and uncheck Appear in Menu before you safe the new category. When you create the category, copy the Category Slug down. You will need this to get to your hidden page. Go to where you created the page and paste the slug at the end of the URL.
So lets say I created a category called Hidden Page with the slug of hiddenpage. I will then click on events from the main menu. (sample.apwa.net/events/chapter/) I will then replace chapter/ with hiddenpage to the end of my URL and press enter. You should now be able to edit the page and add your file.You will need the URL so that you can edit the page and so that others may access your content.