PDF of 310 KB for the APL5930, an Anpec low-dropout linear regulator part; listed as a schematic, it is most likely the manufacturer datasheet. Expect pin assignments, enable and power good behaviour, application circuit and feedback resistor formulas. Technicians use it to verify input, enable and output voltages, calculate the expected output on the board, and decide whether the regulator is shorted or dead. Check the package type and marking code on the chip before comparing pinouts.
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 @schematiclaptopramkushwaha. 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.