It is not possible just for a single specific document, but you can schedule the Billing Due List (SDBILLDL program = VF04 transaction) to run in background with a variant even every 2 min. and this will create a billing document for all the eligible deliveries. (This will most likely include only those with PGI.)
Naturally, the output type for the billing document must be configured to be printed immediately. This is all SD configuration and has nothing to do with ABAP whatsoever. Redirect this request to your SD specialist.
