PackIt was a file bundling, compression, and encryption utility. Although it was very popular for a number of years, it was ultimately displaced by StuffIt (original name, huh?).
Here is a disk image for PackIt III, which you can use this with vMac, a Mac+ emulator, or any other program capable of running the early versions of the Macintosh OS.
For the curious, the source code for PackIt III can be found here.