The file, a 28.4 KB PDF, is named 2SK3485 and catalogued as a schematic; the name is a JIS semiconductor number, so treat it as a short datasheet. Devices prefixed 2SK are N-channel field-effect transistors. Technicians refer to such sheets to identify pins, review ratings and confirm package type when a FET has failed. Given the compact size, only essential parameters may be included; verify the physical part marking and footprint, and pick replacements with matching pinout and equal or better limits.
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.