Filed under schematics, this 77.3 KB PDF named 30SLJQ030 is most probably the datasheet for a discrete rectifier, the lowest voltage code among the 30SLJQ files indexed here. The name carries no board or device information. Component documents like this are used to confirm polarity, package and ratings before soldering a replacement into a power circuit. Measure the suspect part out of circuit with a meter in diode mode, then compare its marking with this document to avoid fitting an under-rated substitute.
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.