I know I'm gonna get jumped on (again), but
There is a quick method to determine approximate proper inflation - not all of us have access to mfr specs ... with your trailer loaded as you would on a vacation, etc. This process assumes the tires are cold (driven less that a mile) Take it to an area where you pull straight for a few hundred feet. Take a piece of sidewalk chalk and draw a line across the tread using the side of the chalk. Now, jump in, and pull the trailer for that hundred or so feet. Stop, Look at your chalk mark. Ideally, it will be scuffed evenly across the width of the tread. That would mead that your tires are inflated to what is needed to give you the largest footprint. More scuffing in the center indicates over-inflation, sidewall scuffing - underinflation (that is assuming you pulled straight). It is not scientific, but it works.
I would be hesitant to inflate tire to the max rating on the sidewall. Anything over that and you are stressing the tires beyond what they are rated. When you drive, the laws of science says rotating tires produce friction. Friction in turn creates heat which makes the tires hot. The hot tires in turn heats the air in them, and heated air expands, so your 35PSI after a few miles down the road is now approaching 40PSI. No matter what web mfg website I've visited, everyone of them will specifically state to not air their tires to the max inflation on the sidewall for this very reason.
Case in point, the tires on my truck have a max sidewall pressure of 75PSI. Ford recommends 60PSI. At 60, using this process, the outer 1" of tread does not even touch the road. I lower that to 50PSI, now, only about 1/4" of the outside tread does touch. Even at 60PSI with the 2400Lb pin weight of my trailer, I still leaves the outer 1/4" unscathed. If I were to put the 75 Max PSI, dang, I'd hit a bump and it would take me 3 miles or 3 days which ever comes first to get the backend back under control.
Just my 2 Lincolns (cents)
Larry