File name 2SC3383 points to a JIS-registered NPN transistor, the 2SC prefix denoting a high-frequency type; the 174 KB PDF is most likely its datasheet even though it sits among schematics. No device or board is named. Use the document to read pin assignment, breakdown voltages, collector current limits and gain grades when diagnosing or replacing the part. Any PDF reader will display it. Compare package style and marking with the component on the PCB, since many transistors share similar codes.
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.