Revision 0 of a document for the 2N5087, supplied as a 301 KB PDF and filed in the schematic section, though the naming suggests a manufacturer datasheet. The rev0 marking indicates an initial edition, so a later revision may exist with corrected figures. Technicians use such sheets to verify pin assignment, breakdown voltages and current limits when testing or replacing the part. Any PDF reader will open it; check the case outline against the actual 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.