Schematic PDF named only IO, 397 KB, with no brand, model or board number in the name. The title suggests an IO daughterboard, such as a USB, audio or card-reader board, but the exact device must be identified from the contents. Open it with any PDF reader and compare the board code and revision in the title block with the part printed on your PCB before using it. Once matched, it helps trace connector pinouts, power feeds from the mainboard and the signals running between the boards.
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 @LaptopsBoardview. 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.