Filed as a schematic, this 145 KB PDF is named only 2N6770, a JEDEC-registered semiconductor number. No host device or board is mentioned. The document is most likely a datasheet listing ratings, characteristics and a mechanical outline. Repair technicians use such sheets to confirm terminal functions for in-circuit testing and to verify that a substitute meets the original limits. Check the marking and package on the physical part first, since similar codes can refer to quite different devices.
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.