At 130 KB, this PDF is named for the semiconductor 1SS376; no board, model or brand appears in the name. The 1SS prefix is the JIS designation for a small-signal silicon diode, so the content should be a manufacturer specification with ratings, characteristic curves and package drawing. Use it to read pin assignment and marking before replacing a failed diode or choosing a cross-reference part. Any PDF reader opens it; verify the package size and marking on the PCB match the drawing.
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.