The 2SC2982 is the only information this 147 KB PDF name provides; it is filed as a schematic. Since 2SC is the JIS prefix for NPN bipolar transistors, the content is most likely a single-part datasheet. Such documents list the pin arrangement, absolute maximum ratings, hFE classes and package outline, which matter when replacing a failed transistor in a power supply, amplifier or driver stage. Before ordering a replacement, confirm the package and any gain-rank suffix on the original part, because these are not stated here.
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.