File 2SC2482 is a 211 KB PDF for an NPN transistor numbered under the Japanese JIS system, recognisable by its 2SC prefix. Though filed as a schematic, it is most likely a component datasheet. Repair technicians use such sheets to look up breakdown voltages, collector current, power rating and package pinout. With that information they can source a correct replacement or check a cross-reference, and confirm the lead orientation against the board footprint before soldering the new part.
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.