Very small PDF schematic named only 4kw2, probably a second sheet or variant of a 4 kW power amplifier design, though the name gives no further detail. Open it in any PDF reader to see which stages it covers. High-power designs like this involve dangerous supply voltages, so confirm transistor types, rail voltages and protection circuits on the sheet before you build or repair. Pair it with the matching 4kw document if you have it, as the two likely belong together.
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 @pdf_servicemanual. 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.