PDF document for the 2SC5785, filed in the index as a schematic, though the part number follows the Japanese JIS scheme where the 2SC prefix marks an NPN bipolar transistor, so it is most likely the component datasheet. At 183 KB it probably holds ratings tables, characteristic curves and package outline drawings. Technicians open it in any PDF reader to confirm pinout, maximum voltage and current before fitting a replacement. Check that the marking on the original part matches the number exactly.
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.