This 93.0 KB PDF carries the part number 2SJ258 and nothing else. The 2SJ prefix, under Japanese JIS numbering, indicates a P-channel field-effect transistor, so expect a component datasheet rather than a full circuit diagram despite the schematic category. It is practical for confirming drain-source voltage, current capability, on-resistance and pinout while chasing a shorted rail or dead amplifier channel. Any PDF reader opens it. Verify package and pin order on the board before fitting a substitute.
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.