"Upload attachments to a video" is a separate feature package and may not be available in your VideoManager.
The video asset management provides a way to create different attachments to a video or channel. The management of your video collection can be arranged very comfortably: if, for example, external production companies produce video footage, you can make available additional information to this video or channel- such as invoices, licenses, etc.
Depending on which document types your administrator has set up (see section in the administration manual), you can upload file attachments for this purpose and always replace or delete again.