Welcome, Ajax! Which model did you get? Where are you located? Is this your first trailer?
So the bad news is that the Cruiser manual for your trailer might be unavailable -- the good news is that the manuals were useless -- very generic and uninformative.
The great news is that the manuals for each subsystem -- HVAC, water heater, fridge, and so on -- are available on the website for the manufacturer of each subsytem -- Dometic, Norcold, Suburban, and so on. Just type in the model number of the item, and away you go.
Even if the manual for the precise item is not listed, the chances are good that manuals for virtually identical model numbers are downloadable. These items tend not to change too much over time. (Sometimes they do -- I remember back when my pilot-light water heater was superseded by an electronic ignition, and the manual was pretty different.)
Be sure to ask lots of questions!
2012 Fun Finder X-139 "Boondock Style" (axle-flipped and extra insulation)
2013 Toyota Tacoma Off-Road (semi-beefy tires and components)