Starting from version 4.7, Smart Diary Suite uses a new spell checker, which makes it easy to spell check your entries in your native language.
To add a language, you first need to download the dictionary from this page:
After that go to SDS' installation folder and you'll see a "dic" subfolder there.
Unzip the file there (you can use 7-Zip (http://www.7-zip.org/), for example, to do that) - it should add a .dic and a .aff file to that folder. If SDS is running, close it down and start it up again and your new language should be automatically picked up.
If spell checking is not functioning, please check the Tools -> Options -> Spell Checking settings to make sure the folders are set up correctly. You are also free to move those folders to anywhere on your machine.
Portable edition users: You'll need to download those language files and place them on your USB stick and then also check the folder settings to make sure they point to them.
There is no set limit on the number of languages you can use at the same time and by default SDS comes with both US and UK English language dictionaries. Adding more languages can slow down spell checking a little bit, so please make sure you only add those dictionaries that you'll be using.