Named 2SC2859, this 192 KB PDF is indexed among schematics but probably holds the datasheet of a JIS-numbered NPN bipolar transistor, as the 2SC prefix suggests. The file name carries no further detail about package, maker or revision. Technicians open such sheets in a standard PDF viewer to check pinout, voltage and current ratings, dissipation and hFE before replacing a suspect part. Also compare the package outline with the board, since the same base number may exist in several packages with different lead orders.
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.