Hello James and getevrybyte,
In order to access encrypted file, some form of the AxCrypt software must be available. As mentioned, there is a stand-alone version that can be included on the thumb drive.
To decrypt a file, you also need access to an AxCrypt ID (key) that it has been shared with, or the original password it was encrypted with. The person encrypting the file can share the keys to the file using AxCrypt, without sharing any passwords. See https://www.axcrypt.net/ for details and instructions.