Covering the 2SC5713 transistor, this 159 KB PDF is most likely a component datasheet; 2SC is the JIS prefix for NPN bipolar devices. The file name offers nothing beyond the number. Repair use is straightforward: confirm emitter, base and collector positions, read the collector-emitter voltage and current ratings, and compare thermal limits when choosing an equivalent. Make sure the marking on the faulty component really reads this number before depending on the values inside.
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.