Catalogued as a schematic, this 45.8 KB PDF is named after the 2SC5503, a part number in the Japanese 2SC series used for NPN bipolar transistors. A file this small is almost certainly the component datasheet rather than a board diagram. Expect pinout, package outline, absolute maximum ratings and electrical characteristics. Technicians use such a sheet to confirm a replacement transistor, check collector-emitter voltage and current limits, and identify the base, collector and emitter pins before testing with a multimeter in diode mode.
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.