PDF of 164 KB catalogued as a schematic and named 28F020 with a trailing underscore, which usually marks an alternate copy of the same part document, possibly from a different vendor or edition. The 28F020 code belongs to the 2 Mbit parallel flash series. The name gives no brand or package. Expect pinout, command set, programming voltage and timing tables. Compare with the other 28F020 files in the index to see which edition matches the chip marking on the board before programming it.
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.