A 240 KB PDF whose short name, 42vforisa, gives little away; it seems to reference a 42 V specification, possibly related to an ISA bus or a part family, but that cannot be confirmed from the name alone. It is indexed as a schematic. Open it in any PDF reader and check the title block or header to see which device or component it actually describes before relying on it for tracing circuits, identifying pinouts or comparing voltages against a board under repair.
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.