The 2SC5171 named in this 169 KB PDF is a JIS-style part number, where the 2SC prefix denotes an NPN bipolar transistor for high-frequency applications, so the content is probably a component datasheet despite the schematic label. The name offers no further details. Open it with any PDF viewer to look up pin order, ratings and characteristic curves. It is handy when a transistor tests open or shorted with a multimeter and you need to judge whether an equivalent part will safely fit.
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.