PDF specification, 135 KB, for the PC2404LRS-AJB-B character module. The digits correspond to 24 characters across 4 lines, and the AJB-B suffix selects a particular option combination and revision B. Expected contents are the pin table, electrical characteristics, backlight ratings, controller command set and outline drawing. Service technicians use it to check supply and contrast voltages, interpret the parallel bus signals with a scope, or find a fitting substitute display. Match the full part code printed on the module before using its values.
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.