These TreePad editions:
TreePad Business Edition,
TreePad X Enterprise Server (multi-user)
TreePad X Enterprise (single-user)
support spell checking in over twenty languages.
By default, they come with the American-English dictionary.
Dictionaries for the other supported languages can be downloaded from this page free of charge:
German-gt3 - ("Old" Std German)
GermanNew-gt3 - ("New" Std German)
Technical (Mathematics, statistics, computing, etc.).
King James Bible + Apocrypha
To install a new dictionary, simply follow these four steps:
(1) Download the dictionary zip file to your harddisk.
(2) Open it with a zip program.
(3) Extract the .adm file (the dictionary) and copy it into the TreePad program directory.
(4) In TreePad itself, using menu/tools/configure spell check,
enable the new dictionary by clicking on the associated check mark.
Please also see this screen shot: