Plain-named 2N3905 document in PDF format, 62.6 KB, catalogued with schematics but most likely a one-part datasheet. No other information such as manufacturer or version is carried by the name. Technicians open it to verify lead assignment before diode-mode testing, confirm voltage and current limits, and compare characteristics when choosing an equivalent. As with any multi-sourced 2N number, check that the package and markings on the board correspond to the drawing before replacing the component.
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.