Component datasheet in PDF form for the 2N5458, an N-channel junction FET usually found in TO-92 packages, catalogued here as a schematic-type document of about 130 KB. The name gives only the part number, so the issuing manufacturer and revision are not stated. Technicians open it in any PDF reader to confirm the pinout, check gate cutoff voltage and drain current ranges, and choose a replacement. JFET pin order differs between makers, so check the drawing against the marking on the part before soldering.
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.