You are only able to upload photos from an iPad to the dropbox in your course. Other saved files from outside the photos folder cannot be uploaded.
The recommended way is that you email the file to yourself and then upload to the dropbox from a laptop or desktop.
You may also consider using the options below.
Option 1: Use Textilus App for text based documents (essays / worksheets): Use the Textilus app to create your document. The paid version can also work with images inserted into a document. Once it is created and you have completed your work, click the "Send to Photos" option.
Option 2: Use CamScanner App and the camera as a document scanner. In some cases sketches, graphs, math problems where you show you work it is best to work the problem on paper and then take an image of it with the iPad camera. We recommend using CamScanner, a free app for all devices.