Archive for Apple logic board 820-1381; the name gives nothing beyond the board number, so the model, revision and document type are not stated. At about 1 MB it is the size of a typical PDF schematic, though that needs checking after extraction. Apple numbers its main logic boards in the 820-xxxx series and prints that code on the PCB. Compare it with your board before using the drawing to trace power rails, follow signal paths or decide which component is pulling a rail to ground.
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 @Mac_Shematic_Santale. 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.