Component document for the 2SC4809 transistor, filed under schematics but by its name and small size most likely a manufacturer datasheet. The 2SC prefix follows the Japanese JIS scheme for NPN transistors, and the _E suffix probably marks an English edition. A technician would open the PDF in any reader to check pinout, package, maximum voltage and current ratings and hFE before fitting a substitute. Compare the full marking on the part with the number here, because suffix letters can change gain class or package.
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.