PDF document of 238 KB covering the 2N4398 device, with an RE suffix in the name whose meaning is not stated, possibly a reissued or revised sheet. It is catalogued as a schematic but is most likely a manufacturer datasheet for a JEDEC-registered 2N part. Any PDF reader opens it. Use it to read absolute maximum ratings, pin assignment and package outline when testing or replacing the part, and verify the marking on the actual component, since second-source versions can differ in package details.
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.