I designed the pledge reminder in MsWord, created one using RE NXT merge fields and use tables to pull all the information and get a grand total of pledges. Best part made sure it fits #10 window envelope and can also be saved as PDF to send by email as well.
I do not use Mail>Reminders at all because of the functionality due to having separated gifts on each printed paper and mail all in one envelope is pointless, waste of paper and costs.
All the different pledge dates, campaign, appeals, amount and grand total in one invoice. Same applies to creating statements too and paid pledges (cash).
how many merge fields do you have going into the table.
it can be done but not by default in RE NXT.
Some methods: