What you're seeing is more likely to be result of the number of pages you're creating and the repagination overheads that imposes. Try working in draft layout view and disabling background pagination.

Nonetheless, you cannot reasonably expect Word to work as quickly with such lengthy documents as with short ones. And, if you think Word is slow, perhaps you should compare its performance with other word-processing & text-editing programs (e.g. Notepad, Wordpad)...

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]