I ordered my trailer with a ladder, however it was shipped without one.
My dealer got Jayco to put a ladder in a trailer being shipped to him and when it arrived he installed it. No problem.
The backing for a ladder should be in your trailer if that is an offered option.
2012 Toyota Tundra 5.7 Litre DoubleCab
6 speed, 4.30 Limited Slip, Tow Package
2013 Jayco White Hawk 27DSRL
2010 Jayco JayFlight 26BH sold
Yamaha EF2000is Generators (2)
1996 Honda CB750 Nighthawk