This 26.1 KB PDF, placed in the schematic section, is named after the 2N6517, part of the JEDEC 2N numbering used for discrete transistors and similar devices. The name states no other detail, so the content should be the standard datasheet: package type, pin layout, ratings and electrical characteristics. Use it to identify leads before replacing the part, to check in-circuit measurements against expected junction behaviour, and to pick an equivalent. Confirm that the package on the board matches the outline shown.
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.