I would like to cancel a pending Order but the "Cancel Document" button is absent on the Order screen. The Order was paid by a batch.
Orders paid by a batch can not be cancelled individually.
To cancel a pending Order that was paid via a batch you have to cancel its Offline Payment, e.g.:
Top > Billing Director > Receivable > Documents > Orders > Order #12345 > Payment History > 11111 Invoice > Paid by > 22222 Offline Payment > Cancel Document
Please note that if you cancel the Offline Payment #22222 it will not only make it possible to Cancel the Order #12345 (the "Cancel Document" button will appear on the Order screen) but also reopen the Invoice #11111, and the balance of the customer account that owns a subscription for which the Order #12345 was issued will be reduced for the invoice sum.
Thus, please be careful while cancelling Offline Payments for it will affect customer's balance.