This 129 KB PDF, named 30WQ06FN and filed as a schematic, appears to document a single semiconductor, most likely a Schottky rectifier in a surface-mount package, rather than a circuit board. The numeric middle section of such codes normally denotes the voltage class. Use the sheet to check reverse voltage, forward drop and the land pattern when replacing a part on a DC input or converter stage. Verify the code on the actual part, including the FN suffix, and test the old component out of circuit to confirm it really failed.
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.