Covering the 203CMQ080, this 144 KB PDF is most likely a datasheet for a CMQ-series Schottky rectifier rated, judging by the 080 suffix, at 80 V. No device or board is named in the file title. Repair work uses such documents to verify forward voltage, average current, avalanche or surge limits and package outline before fitting a replacement in a switching power supply output. Any PDF reader opens it. Check that the original marking matches exactly, as CMQ and CNQ parts may differ mechanically.
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.