From the docs:
https://www.tessituranetwork.com/Help_System/Content/Ticket%20Printing/Reprinting%20Tickets.htm
Reprinting Individual Tickets
If only some of the tickets in an order need to be reprinted, this can be done from the Sub Line Items tab.
Note: Attempting to reprint an individual performance sub line item that is part of a composite ticket will reprint the whole composite ticket, generating a new composite ticket number and new ticket numbers for all component performance seats (not just the selected performance sub line item).
Click on the desired sub line item to select it. Multiple sub line items can be selected using Ctrl+Click and a range can be selected using Shift+Click.
I didn't follow this exactly: I selected the lineitem, then went to the sub lineitem page, checked that the right tickets were selected, then went to print, selected reprint and chose 'Request PAH Reprint", but the entire order was reprinted.
following!