PDF document for the 2SC4435, catalogued as a schematic but named after a discrete semiconductor part number rather than a board. Under the Japanese JIS scheme the 2SC prefix marks an NPN bipolar transistor, so the 92.2 KB file is most likely a datasheet sheet for that device. Technicians use such a sheet to confirm pinout, package and maximum ratings before fitting a replacement. Any PDF reader opens it; compare the marking on the original part with the document before choosing a substitute.
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.