The Custom Dictionary is just a list of words in plain text. Simply open
custom.dic and paste in a list of Words and sort into alphabetical order.
However, don't exceed the 1000 entry file size.
Comments below apply to the English spell checker for Word 2000 and
later; others may differ...
There is no limit in Word 2000 and later. One user reported using a
custom dictionary containing over 160,000 words.
When adding words, you should generally use lower case. If you use any
capital letters in the entry, the entry will match only text words
with the same capital letters.
It is possible to add plural forms of initialisms (acronyms) to the
custom dictionary, e.g. "PDFs". This is the only way to keep them from
being flagged.
Adding hyphenated words is tricky. If Word thinks that some of the
pieces are correctly-spelled words, it will probably not allow you to
add the entire hyphenated "word". If none of the pieces are
recognized, it may allow you to add the item.
The dictionary will also accept words with slashes or with straight
apostrophes. Other punctuation may or may not work.
Avoid any characters not in the code page 1252.
A word may not contain more than 64 characters.
Sorting is not required and duplicate entries do not hurt; the next
time that you add a word using Word's dialogs, the list will be sorted
and duplicates will be eliminated by Word.
Bob S