Upper tool bar  FILE>>>>>Print Options>>>  then this is the tricky part...it opens with "Print Functions" as the default....Right above Print Functions...click on Global Print Options>>> Control which letters print.and there you go.  I do a Custon Client Specific letter for each client, but you still have to click on Standard Client Letter and Custom Client Specific letter to get the custom one to print.  This is also where you tell it when to print the engagement letter.

I copy my previous year's standard letter over to current year, because over the years I have tweaked and formatted it too look much more professional and informative than the simple generic letter available.