Go to My employees and select the employee concerned by the document.
On the left panel, check for the employment section, and click on documents.
By selecting add documents, you open a pop up inviting you to either upload a document yourself or request your employee to do so.
In both cases, you can tick the boxes to determine who will sign the document:
Nobody (this option deselects the other too)
You must tick both the employee and checkboxes if you need both to sign the document.
Track the document
If your employee is requested to perform an action (uploading a document and/or signing it), you will be able to track the process from the document tracking tab available in the HR section.