How to secure items on Purchase Orders or have security on Document Styles

Summary:

We have 2 different Item Classes > Trade and Non Trade and assigned different items to it. Our customer needs security that Buyers can only manually enter Purchase Orders for Non Trade items. But they also need to be able to monitor the interfaced Trade Purchase Orders. 

What we tried: 

- Created 2 different Inventory Organizations (1 for Trade and 1 for Non Trade) to separate the Trade and Non Trade items for usage. 

- Created a new Data Reference Set for Non Trade Locations. 

- Created 1 Locations and assigned 1 to the Non Trade Locations data reference set. Also assigned the Non Trade location to the Non Trade inventory organization.