A 130 KB PDF filed as a schematic, titled 28C16A, the A revision code of the 28C16 16 Kbit parallel EEPROM. The name gives no manufacturer or package details. It should contain pin assignments, write timing, supply voltage and endurance data. Technicians rely on such sheets when reading or programming small configuration memories on older equipment and when comparing against 2716-style EPROM pinouts. Check the exact part marking on the component and keep a copy of the original contents 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.