This 183 KB PDF takes its name from the 2SC2840 and is indexed as a schematic. In Japanese JIS designations, 2SC means an NPN bipolar transistor, so the document is probably the device datasheet, with no maker or revision given in the name. Typical uses include checking pinout before in-circuit diode tests, comparing maximum collector-emitter voltage and current with a proposed substitute, and reading package dimensions. Confirm that the original component marking and footprint agree with the data before soldering a replacement.
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.