Listed as a schematic, this 53.9 KB PDF is named only with the code 55HQ030, and no device, brand or board revision is given. The code follows the style of a discrete power semiconductor part number, so the file most likely holds a datasheet with ratings, a package outline and characteristic curves. Technicians use such sheets to choose a replacement part and confirm its pinout. Compare the marking on the actual component with the document heading before you swap a part based 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.