Indexed under schematics, this 181 KB PDF named 28512 most likely documents a 28-series 512 Kbit parallel EEPROM, though the name does not confirm the manufacturer or package. Such a datasheet gives pin assignments, write timing, page write behaviour and data protection features needed when reading or programming the chip in a universal programmer. Its size equals that of the plain 28256 file, so check that the content really matches the title. Save a backup of the original data before writing.
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.