Component document covering the 2SA1371, a JIS-numbered PNP transistor; under that system the 2SA prefix denotes a high-frequency PNP device. The 140 KB PDF is filed as a schematic, but a name made only of a part number points to a manufacturer datasheet. Technicians open it in any PDF reader to check the pin order (E, C, B), the case style and the absolute maximum ratings. Compare the device code printed on the body, often shortened to A1371, before choosing a replacement.
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.