With regards to office documents, be aware that many of today’s office-type applications syncronize your documents directly in the cloud (on the internet). This is a great feature for backup and assurance that you can access your documents from any of your computers, devices, and from multiple locations (I myself love this feature for non-confidential documents). As soon as you enable any online, internet, or cloud syncronizations features your documents can easily end up read or copied if a surveillor has access to the system storing them or can survey the network (internet) connection between you and them. I’ll go more into encryption in the next section, but for now just keep in mind that anything you send outside of your own (very) small circle of control is subject to being intercepted or copied by others.
Intending to add notes about Dropbox, Box.net, Google Drive, SkyDrive, and others.
Intending to add notes about Boxcryptor.