For the 2SK2313 transistor, this 419 KB PDF is filed as a schematic but is expected to be a datasheet, since 2SK is the JIS prefix for N-channel FETs. It should contain maximum ratings, typical characteristic curves, switching times and package dimensions with pin assignment. A repairer relies on this data to check whether a measured short is plausible, confirm orientation when refitting, and pick a suitable substitute. Verify the marking on the component, including any suffix, before trusting the figures.
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.