I select “Share” on the file and enter Bob’s email address. This tells Axcrypt that the file from me can be decrypted by Bob(?)
The simplified technical explanation is that AxCrypt re-encrypts the file with Bob’s public key (which AxCrypt store).
After you’ve used the “Share” feature you’re free to upload the file to Dropbox (or send by email) but not before. If you sent the file to Bob before you’d shared it, he’d be unable to access it because it would only have your encryption on it.
Since Bob set up an Axcrypt account with his own password, he can now open the file I shared with him through Axcrypt… correct?
As long as Bob has an AxCrypt account then you can forget about public and private keys. Just select “Share” and everything else is handled by the software. All you need to know is Bob’s email address.
You use your password, Bob uses his. Remember that AxCrypt don’t know your password (so don’t lose it!).
If you want to unshare it, you can. Obviously he may have printed or photographed your file so don’t rely on this feature in circumstances where you can’t trust the recipient!
There’s a little video tutorial here –