Additional spell-check dictionaries are available at: http://addictivesoftware.com/dl-dictionaries.htm
Download the language dictionaries you wish to install in Personal Historian 3. You will need to open the zip file and copy and paste the contents into the Personal Historian 3 program file. You can also just extract the zip file into the program folder.
Once the additional dictionaries are in the Personal Historian 3 program folder launch the Personal Historian 3 program. Go to: Tools >Program Options> General> Spell Check Options..> Language> check boxes next to additional dictionaries you wish to use. Click OK a couple of times to save settings.