The 330 KB PDF here carries the part number 2SC2551, a JIS-registered NPN transistor designation. Although it is listed as a schematic, the file name points to a datasheet with electrical characteristics, ratings and package drawings. It is useful when a failed transistor has to be identified or cross-referenced. Check the collector-emitter voltage, collector current, power dissipation and hFE grade against the circuit, and confirm the pin arrangement from the outline drawing before soldering in a 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.