Named 15ctq035 and sized at 168 KB, the PDF is indexed as a schematic. The designation follows the International Rectifier or Vishay dual Schottky rectifier pattern, so it is probably a datasheet giving the common-cathode or similar pin configuration, reverse voltage, forward current and thermal resistance. That is useful when diagnosing a low-voltage output rail on a power supply or picking a matching replacement. Compare the marking on the real part carefully, as neighbouring codes differ in voltage grade.
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.