A small PDF of 147 KB catalogued as a schematic, although the name 1N3288A follows the JEDEC 1N registration used for discrete diodes, so it is most likely a component datasheet rather than a board drawing. The A suffix marks a variant within that part number. Technicians use such sheets to confirm ratings, package outline and polarity before fitting a substitute. Any PDF reader opens it. Check that the marking on the faulty part really matches this number, since similar codes can belong to different devices.
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.