Part datasheet, most likely, for the 2SK2837, provided as a 426 KB PDF and indexed as a schematic. Under Japanese JIS component naming, 2SK denotes an N-channel field-effect transistor. The sheet serves to identify terminals, look up voltage, current and power ratings, and support substitution decisions when the original part is unavailable. Any PDF reader will open it. Before relying on it, make sure the marking on the failed transistor really reads 2SK2837 and the package outline matches.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.