Listed in the schematic category, this 139 KB PDF named 27c020 is in fact best read as a datasheet for a 27C-series CMOS EPROM. The file name offers no brand, board or equipment detail. Technicians open it to confirm pin assignments, supply voltage, access time and programming conditions. That matters before dumping the chip, burning a replacement or selecting the right device entry in programmer software. Different vendors' versions can differ slightly, so match the logo and suffix on the IC.
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.