Datasheet-style PDF for the 2SA1858 semiconductor, catalogued here under schematics, with an _E suffix in the name that likely marks an alternate edition of the document. Under the Japanese JIS numbering system, the 2SA prefix identifies a PNP bipolar transistor. At 40 KB it is probably a short sheet of ratings and package drawings. Technicians use such a sheet to confirm pinout, maximum voltage and current before fitting a substitute on a board, and should compare the body marking on the original part first.
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.