Hi Charles,

You're likely using in-built features of Word to encrypt those documents; this tends to encrypt the payload inside the Word file format wrapper. With JPG or PNG at least, you're going to need a generic approach to encryption, so using openssl or gpg to encrypt the entire file stream and then transmitting that. Pro-PDF tools may have a similar option to Word.

One generic approach that works from Stack Overflow here is to use gpg: https://stackoverflow.com/a/31552829/21120938

* Input/encryption (file to send that needs encryption): gpg --output encrypted.data --symmetric --cipher-algo AES256 image_data.jpg
* Output/decryption (file to decode): gpg --output image_data.jpg.unencrypted --decrypt encrypted.data

You'll be prompted for a password for encrypting the data which you will then find a secure way to transmit to your user who will be prompted for that when they decrypt the file. 

I have tried it on Linux and Windows, and the experience is roughly the same. For Windows installers: https://gnupg.org/download/

I find the subject of encryption really fascinating and its something I want to learn more about and form a habit of doing. That being said I don't use it regularly at work right now and so I am interested to hear about other's processes, and from any corrections/improvements to the above. 

Best,
Ross