Schematic PDF named Z84J, 2.56 MB, with no revision or brand given in the name. The drawing should identify the manufacturer and board code in its title block, which is worth checking first. A technician relies on such a document to trace power rails, check standby voltages, follow clock and reset signals and find parts around a short circuit. It opens in any PDF viewer. Make sure the board marking on the PCB matches the drawing, as related variants of the same platform can differ.
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 @schematicslaptop. 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.