If you want to prevent users from storing certain file types as documents in your file cabinets, please navigate to "Organisation" -> "General" and add the file types you do not want to be stored as "Restricted file types"
To be able to choose those file types, you mus first have defined them by creating "file extension lists"
("Organisation" -> "Files extension lists")

This can only be done for the whole organisation, not for single file cabinets.