The 121 KB PDF is named 45MT160P and sits in the schematic category, with no device, board or revision mentioned. Its format looks like a power module or semiconductor part number, so the document is likely a datasheet describing terminal layout, internal circuit and maximum ratings. Use it in any PDF reader when identifying connections on a power stage or picking a substitute. Check that the marking on the module you are working on matches this code exactly before relying on it.
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.