The name 243NQ gives only a part family prefix with no suffix, so this 45.4 KB PDF probably covers a whole series of power rectifier devices in one datasheet, despite its schematic category. A family sheet typically lists each voltage grade in a table. Use it when identifying a module from its markings, checking its limits or finding a suitable substitute. Open it in any PDF viewer. Read the complete code on the component, as the missing suffix here means you must pick the right row yourself.
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.