This 30.5 KB PDF is titled with the 2SA1526 part number and indexed as a schematic, though it is most likely the transistor's datasheet. Under the Japanese JIS scheme, 2SA parts are PNP transistors for high-frequency use. Technicians open such sheets in a PDF reader to identify pins, confirm package type and read breakdown voltages, current limits and dissipation before testing or swapping a component. Compare the marking on the original transistor with the document to avoid fitting a wrong variant.
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.