If you wonder how much a standard four-drawer filing cabinet weighs when full, the most precise answer may be a vague: "a lot." A regular, plain steel four-drawer filing cabinet, when empty, can weigh up to 150 pounds. Once it's full, it weighs significantly more. According to Conversion Technologies International, once it's filled with paper, upright four drawer filing cabinet may weigh approximately 440 pounds. However, some filing drawer slides can support up to 150 to 220 pounds per drawer, so it's conceivable for the same filing cabinet to weigh over 750 pounds -- 150 pounds empty weight plus four drawers weighing 150 pounds. Lateral files present similar weights but the tipping point is different. Something to plan for.
A 750 sheet ream of paper weighs in at 6lb 11oz. Add empty weight of the wood, folders, and hangars and it gets up there. Tipping toward the user can be dangerous..
The problem aside from selecting the drawer slides, say 220 lbs full extension, is also the cantilever of a full drawer pulled out. A lateral file is worse than a typical foot wide upright. At 36" wide at whatever depth with the top drawer fully extended and a crap load of paper some consideration of weight and center of gravity is warranted.
You will need full extension in order to pull out files. You might want to check the specs of similar sizes to yours from web sources. Cabinet attachment to the wall is something you might also wish to consider.