Indexed as a schematic, this 99.3 KB PDF is titled 2SK2406 and is most probably a datasheet for an N-channel field-effect transistor, as the 2SK prefix indicates under the Japanese JIS numbering system. No other information is contained in the name. Readable in any PDF viewer, it lets a technician confirm pinout and electrical limits, check whether a candidate replacement has equal or higher ratings, and interpret diode-mode readings taken on a suspect device removed from the board.
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.