Catalogued under schematics, this 51.3 KB PDF is named after the 2SC1473, which by the Japanese JIS convention is an NPN bipolar transistor, so it is most likely a component datasheet rather than a board diagram. The _E suffix probably marks an English-language edition. A datasheet like this gives pinout, package outline, maximum ratings and gain figures. Technicians use it to identify the lead order before testing with a meter and to choose a substitute with equal or higher voltage and current limits.
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.