Covering the 2SK2991, this 420 KB PDF is named only by part number, which points to an N-channel field-effect transistor in the Japanese JIS numbering system. Expect a component datasheet with ratings tables, package outline and pinout rather than a full circuit. It is useful when a transistor in a switching circuit has blown and a technician needs to verify its specifications, find an equivalent and check orientation on the PCB footprint before installing the replacement.
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.