Does a password-protected zip file work?
You then have to communicate the password out-of-band, as emailing it would defeat the purpose. It may be hard to read over the phone and you have to trust it was not written down and the file is not then stored/forwarded unencrypted. Explaining the process to someone non-technical may be challenging.
Symmetric crypto is a mess, asymmetric would be great if secure key exchange could be easy. If only the software was as ubiquitous as zip handling is in the OS.
The recipient's identity is the key to opening the content - no need to communicate anything out-of-band. Depending on the file format chosen, you get DRM features limiting granular actions on the file beyond view/edit.
To open the protected files, your recipients will have to download/install the (free) app from Microsoft. This is generally pretty painless.
Definitely worth checking out, especially good for consultants' workflows.
This is the product page: https://www.microsoft.com/en-us/cloud-platform/azure-informa...
Its not elegant, but in the end I find it reasonably good compromise between security and practicality.