Catalogued as a schematic, this 93.1 KB PDF is named only after the part number 2SJ281, which follows the Japanese JIS scheme where the 2SJ prefix denotes a P-channel field-effect transistor. The document is therefore most likely a component datasheet rather than a board drawing. Technicians use such sheets to confirm the pinout, package, voltage and current ratings and on-resistance before fitting a replacement. Any PDF reader opens it. Check the marking on the original part, since substitutes must match polarity and pin order.
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.