Apple iPad 4 logic board view in .pcb format, around 21 MB. The file maps the component placement and nets, so a repairer can click a net to see every part connected to it, find where a rail can be measured and identify parts near a damaged area. The .pcb boardview format is readable in tools such as OpenBoardView or FlexBV, depending on the variant. Confirm the device is the fourth-generation iPad, since earlier and later boards differ in layout and part numbering.
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 @boardview. Enginerys does not host this file.
How to open a .pcb file
In repair archives a .pcb is typically an XZZ (XinZhiZao) boardview — popular for phones and recent laptops.