A 47.6 KB PDF carrying the JIS part number 2SA1988, a PNP bipolar transistor according to the 2SA prefix. Listed in the schematic section, it is most likely the device datasheet; maker and package are not stated in the name. Technicians use such a document to confirm which pin is emitter, base and collector before probing, to check voltage and current limits against the circuit, and to choose a substitute with matching polarity and footprint.
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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)