At any time should you be able to upload a document and for certain leave types it is mandatory to upload documents; e.g. for Certified Sick Leave, Paternity & Maternity Leave.
If it is not possible to upload a document, it could be because of two issues:
1) The file name cannot be more than 50 characters. Reduce the length of the file name, and then try again, OR
2) The file name cannot contain ‘special’ or ‘illegal’ characters like French accents (such as é) or Spanish tilde (~). Change the file name, and then try again.