Listed as a schematic, this 412 KB PDF carries only the part number 2SK2845 in its name. The 2SK designation follows the Japanese JIS convention for N-channel FETs, so the content is probably a manufacturer datasheet rather than a board drawing. It is useful for identifying gate, drain and source pins, reading maximum ratings and checking a suspected shorted transistor with a meter. The name states nothing else, so verify the package and the full marking on the PCB part before relying on it.
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.