The "DOCUMENTS" tab on the "Leads profile" or under “View Lead” page is for you to upload files and save them for the Lead. You will be taken to the View Lead page whenever you click on a lead's phone number anywhere in Ringy or when clicking on a lead's response in the Inbox.
Additionally, they are not sent to the client unless you select the "SEND EMAIL" tab, and select the "*paperclip icon* Attach Lead Documents" found below the email body. You will then choose the appropriate documents you uploaded previously to send to the lead via email.