Here the 41.7 KB PDF is labelled with the part number 2SA2023, a PNP bipolar transistor under the Japanese JIS 2SA designation. The document is probably the component datasheet, although the catalogue lists it as a schematic. The name gives no further details. Technicians check such a sheet for pin assignment, maximum ratings and the package marking, which on small SMD parts is usually a short code, so the fitted part can be identified and replaced with an exact match.
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 @cyberlanelectonik. 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.