The name 31DQ05 suggests a discrete diode part number, so this 75.9 KB PDF, although catalogued as a schematic, is probably a single-part datasheet. It appears to be a sibling of the other 31DQ files in this set, differing in the suffix that typically marks the voltage grade. A repair technician would open it in any PDF reader to check polarity marking, maximum reverse voltage and forward current before replacing a burnt rectifier. Make sure the replacement grade is equal to or higher than the original rating.
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.