The Order Details form is a form that sales reps and B2B Storefront customers can access from the Cart view of their order. This form contains fields that they can fill in with additional information about the order. This information is saved along with the order and can be printed on the Order PDF form sent.
If you wish to make a field Mandatory on the Order Details Form this means the order will not be able to be submitted until the user opens the form and fills in this field.
When the field is mandatory it is marked with a red star on the form and users will receive a warning message if they try to submit an order without filling in this field, the form will automatically open and once they enter a value in the field and save the order will be submitted.
In any "Header" form layout (this refers to the Order Details form) you may be editing throughout the Pepperi settings, click on the edit (pencil) icon next to the field heading and select the check box for "Mandatory".
(Selecting "Read only" will make the field non-editable.)
Here is what it will look like on the form :