When you send multiple documents to multiple recipients in one transaction, you can choose to set visibility per signer. This feature is useful when a recipient only needs to sign one document (out of many). The other documents that are not relevant to that recipient are therefore not shown.
You create a new transaction, add the documents and recipients, click on "Create transaction" and then enter the "Designer" screen. To the left of the "Send to Sign" button you will find the following icon:
Under this button you can set the visibility per signer (see image below).