Named after the 2SC1383, this 51.4 KB PDF is listed as a schematic, yet the JIS prefix 2SC denotes an NPN bipolar transistor, so expect a part datasheet. The trailing _E most likely means the English edition of the document. Typical contents are the absolute maximum ratings, electrical characteristics, hFE classification and package drawing. Repairers rely on such sheets to verify lead order before in-circuit diode checks and to confirm that a substitute transistor meets or exceeds the original voltage, current and power limits.
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.