An 86.7 KB PDF for the 2N3903 with a Sam tag in parentheses, which may indicate a particular manufacturer's edition, although the name does not spell it out. Indexed as a schematic, it should be a datasheet for this JEDEC part. Typical use is confirming lead identification, reading voltage and current limits and checking gain figures before replacing a suspect device. Because other 2N3903 sheets exist here, compare versions and match the package on the board before relying on the pinout.
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.