PDF schematic of about 979 KB carrying only the code KL2D, with no brand, model or board number given. Codes like this are often internal project names used by board makers, so confirm the match by comparing the title block of the document with the markings on your PCB. Once matched, a schematic lets you trace voltage rails, follow power-on sequencing, read signal names between chips and identify component values. Any PDF reader opens it; check the revision before relying on individual parts.
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 @alischematics. 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.