Datasheet for the 2N3442 in a 136 KB PDF, filed in the schematic category. The r7 ending in the name likely marks a document revision number, though the name does not confirm this. It covers the specifications and package drawing of this 2N-numbered transistor, used when checking maximum voltage and current, gain and lead order before replacement. Any PDF reader opens it. Because a 2N3442RE copy of equal size also exists, the two may be the same sheet under different names.
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.