A 24.2 KB PDF for part 2SC5287, an NPN transistor by Japanese JIS designation. Though tagged as a schematic, a part-numbered file like this is normally a datasheet giving ratings and pinout. Its small size points to a concise one or two page sheet. Technicians rely on such documents when checking a transistor for shorts, confirming lead order, or selecting an equivalent part with suitable voltage and current ratings. Compare the body marking on the fitted part with the document.
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.