If you wish to keep a document private, you can use Simredo's encryption function.
First, create or open the document which you want to encrypt. Then select 'Save as' from the File menu. The Format Conversion dialogue will appear. Select Encrypted from the list of formats and click on OK.
Simredo will ask you to type in an encryption key. The word (or sentence) must be at least 8 letters long. Type the same key into both text fields. If they are not the same, encryption will not succeed.
After you've typed in the key, click on OK. The 'Save File' dialogue will appear. Enter the file's name and save it. (You should overwrite the unencrypted original.)
When you open an encrypted file, Simredo automatically recognizes that the file is encrypted, and displays the dialogue at right. Type in your key word or sentence and click on OK. Your original document will appear.
NB: Your key must be exactly correct, and upper and lower case matters. For example, if you use the key 'Jar Jar Binks' to encrypt a file, you cannot decrypt it with 'jar jar binks'.
If you are interested in the encryption algorithm, there is a description here.