Small PDF datasheet of 61.5 KB for the PG12864-Q display, a 128 by 64 dot graphic LCD module in the PG series, variant Q. Documents of this kind give the connector pinout, controller interface signals, power and contrast supply requirements, and drawings of the glass and frame. Repair staff rely on it to verify that the right voltages reach the module, to check chip-select and reset lines, and to judge whether another variant can replace it. The Q suffix must match the part label on the unit.
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.