You need something to grab above deck level to help pull yourself up. Picture climbing onto a roof from a ladder - it's a LOT easier if the ladder extends a couple of feet above the edge of the roof. We were recently at Mystic Seaport and tied to a stone wharf. There were iron clips in the large stones for climbing, but nothing up top to grab. We ended up moving to the floating dingy dock so the wife could get on and off the boat without beating herself up.
The pull down ladder should work fine if you locate it at the shrouds or the backstay.