Boardview for the Apple A1278 MacBook Pro 13-inch built on logic board 820-3115 revision A, packed in a small 152 KB zip. Apple prints its 820-xxxx logic board numbers on the PCB, and the revision letter matters because layouts change between revisions. Open it in OpenBoardView, FlexBV or a similar viewer to look up components, follow nets, find test points and pinpoint shorted rails. Compare the board number and revision on your logic board with 820-3115-A before you start measuring.
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 @cynetitsolution. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.