Very small at 10.8 KB, this PDF named 1n6778 looks like a brief datasheet or spec page for a JEDEC 1N-numbered semiconductor, despite being indexed as a schematic. The name states only the part number, so the device class should be confirmed from the document itself. Such pages usually give maximum ratings, key electrical characteristics and the package. Use it to verify a part marking and compare ratings when choosing a replacement, and check pinout and package outline against the component on the board.
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.