A PDF filed under schematics but named after the 2SK404, a part number in the Japanese JIS semiconductor scheme, where the 2SK prefix marks an N-channel field-effect transistor. At 78.5 KB it is most likely a component datasheet rather than a board diagram. Technicians use such sheets to confirm pinout, package, voltage and current ratings before choosing a substitute. Check the marking on the faulty part against the document, since suffix letters and manufacturer prefixes can change gate threshold or package style.
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.