spell checking

I am creating a large docbook manual using docbook and XEP to create 
html and pdf output.

Does anyone have any recommendations for spell checking.  As this is a 
technical manual, I will have to
add to the dictionary.

I have created an RTF output and loaded the result into  MS Word, but 
this method is clunky as the document
is over 1000 pages and I have to spell check piecemeal due to 
performance issues.

TIA

Paul