PDF schematic of 2.10 MB whose name, apparently Persian for something like introduction to circuits, gives no device, brand or board number. Its contents must be opened to find out what hardware it covers. A schematic is normally used to trace power rails and signal paths, identify components on a shorted line and understand the power-on sequence of a board. Any PDF reader opens it. Before relying on it for measurements, compare the board number and revision shown in the drawing with the PCB under repair.
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 @mobile_jump2. 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.