Documents and pictures can be added to customer details via the Stock+ App. Within the customer details screen, click the Documents tab, this will then display any current Documents attached and allow you to add new Documents:
Using the 
icon for document uploads or the icon to take pictures. Documents can then be saved against a customer record and will appear to view within the Documents tab for future reference.
Select your Document name and select a Category from the drop. Once added, click save.
PLEASE NOTE: Documents cannot be deleted from the Stock+ application once added.
You can also use the camera icon to take a picture to then add as a document itself.