At 168 KB, the document covers part 2SC5692 and is filed as a schematic. The 2SC prefix follows the Japanese JIS convention for NPN transistors intended for high-frequency use, so expect a datasheet with ratings, characteristic curves and a package drawing. The file name states nothing else: no manufacturer, revision or package. Technicians use such sheets to confirm the pin order and limits of a failed transistor and to judge whether a replacement part is a safe swap. Any PDF viewer opens it.
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.