RAR archive for an X450LD board labelled revision 2.1, judging by the name, which follows ASUS model naming. The name does not say what is inside. At 152 KB it is most likely a boardview or other small service file rather than a full schematic set. Extract it first and identify the contents. A boardview opens in a viewer such as OpenBoardView or FlexBV, where you can locate parts, nets and test points. Before trusting any pinout, check that the revision silkscreened on the PCB really reads 2.1, because layouts change between revisions.
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 .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.