Small Apple schematic PDF of 669 KB whose name reads only 4 g, which most likely refers to an iPhone 4 family model, though the exact device and board revision are not stated and should be confirmed by opening the document. A phone schematic like this is used to follow power rails, trace charging, display and audio lines, and identify components on a rail suspected of a short. It opens in any PDF reader; check the logic board markings against the drawing before relying on part references.
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 @Schematics_Mobile. 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.