Short-named schematic PDF labelled only M750, 847 KB in size, with no brand, model or board number given. The code looks like a project designation, but the actual device must be confirmed from the title block inside. Once identified, the drawing can be used to trace power rails, check sequencing signals, find test points and locate components around a short. Always compare the board number printed on the PCB with the schematic revision before trusting values or net names.
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 @alischematics. 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.