PDF for the 2SA1701, a JIS-coded semiconductor; the index lists it as a schematic, yet a bare part number like this is almost always a manufacturer datasheet. In Japanese numbering, 2SA denotes a PNP transistor intended for high-frequency applications. At 144 KB it probably includes characteristic curves along with the ratings table. Technicians open it in any PDF reader to check pin order, collector current and voltage limits, and to judge whether a substitute device is electrically and mechanically compatible.
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.