Bearing only the part code 2SJ264, this 101 KB PDF relates to a P-channel FET, as the JIS 2SJ prefix designates that transistor type. Although listed as a schematic, the name supplies no device model or board number, so the content is presumably a datasheet. It is useful for verifying pinout, ratings and switching characteristics before measuring the part or picking a cross-reference. Any PDF program opens it. Compare the marking and package on the board with the drawing in the sheet before replacing anything.
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.