Indexed as a schematic, this 129 KB PDF bears the code 30WQ10FN, which looks like a surface-mount Schottky rectifier part number rather than a board design. It is probably a datasheet for that part, with the FN suffix likely tied to the package or packing option. The document is useful when sourcing a replacement for a rectifier on a power supply or charging circuit, letting you verify the footprint and ratings. Confirm the body marking matches before soldering in a substitute and observe the cathode orientation shown in the outline 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.