The 152 KB PDF is labelled 2SC5355, a Japanese JIS transistor designation in which 2SC identifies an NPN device of the high-frequency category. Despite being filed as a schematic, it most likely contains the single-component datasheet. A repairer uses it to determine base, collector and emitter, read the safe operating limits and compare gain grades when replacing a damaged part. It opens in any ordinary PDF reader. Confirm that the physical part and its package match this number before relying on 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.