Small 51 KB PDF for the PG320240-C graphic LCD module, the C variant of a 320 x 240 dot series. The limited size suggests a short document, likely the outline drawing plus pin and electrical tables. It helps identify the connector pinout, logic and LCD supply requirements and mounting dimensions when repairing or replacing a panel. Since several lettered versions exist, compare details against the module in hand rather than assuming another variant behaves the same.
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 @acodis_lcd_datasheets_EDID. 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.