Part number 2SC4454 gives this 101 KB PDF its name, and the index places it in the schematic group. Following the JIS convention, 2SC denotes an NPN transistor designed for high-frequency circuits, so the file is most likely its datasheet. Further details are absent from the name. Consult it for the pin map, maximum ratings and hFE classification, and cross-check the marking on the physical device, since small packages often carry abbreviated codes that differ from the full type number.
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.