Small PDF schematic labelled PA 1650 56LC, most likely the circuit diagram of a power adapter given the PA prefix, though the name does not confirm the brand or rating. At 464 KB it is a compact document. A technician uses such a schematic to follow the primary and secondary stages, identify the PWM controller, check feedback and protection parts, and find replacement component values. Compare the model label on the unit and the PCB markings before relying on it.
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 @ShareMan_Electronic_Files. 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.