1. set: Catalog - Configuration - Request Management Configuration - Allow Attachments at Service Option Level be set to Yes
2. set the Attachment Mandatory in the Service Option Level:
a. go to: Catalog - Service Offering - Offering Tab - (choose the Service Offering you want to set the Attachment as Mandatory
b. Click in the right Panel in Definition Tab
c. Choose the Offering and click Edit
d. There is a check box for "Attachment Mandatory"
e. Check that box and save it
Now you will force the Attachment as Mandatory for that Service Option Level.