Hi Jessica,
From where did you open the file for editing originally? Have you saved it properly before you submit it?
As Paul mentioned above, in some cases, corrupted documents are rarely recoverable. Do you have a backup of that file? Or elaborate a little bit about your situation for further assistance.
Regards,
Ethan Hua
TechNet Community Support
It's recommended to download and install
Configuration Analyzer Tool (OffCAT), which is developed by Microsoft Support teams. Once the tool is installed, you can run it at any time to scan for hundreds of known issues in Office
programs.