The 123 KB PDF bears the part number 2SC4644 and nothing else. That makes it a reference for a single NPN transistor rather than a full circuit diagram, despite the schematic category. JIS numbering places 2SC parts in the high-frequency NPN group. The sheet should list breakdown voltages, collector current, hFE ranks and a package drawing. Repair work uses this to confirm pinout and marking, test junctions with a diode meter, and select an equivalent when the exact part is unavailable.
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.