Documents can be added to a contact using the Web Portal, CRM > Contacts > Select the contact that you would like to add the Document to > Scroll down the the activity section of the Contact > Document > +New Document. 

When uploading the Document you can, name the Document, add it to a folder or create a new folder, create a version for the document and even add an expiry that will allow the system to automatically remind you when the document is ready to be reviewed or updated.

Documents within a customer card can be viewed in the app but needed to be added through the Web Portal.