If you can decide which pages you need to send automatically (i.e. on the
basis of the data in the mail merge data source) then you can consider using
INCLUDETEXT fields to include the additional page(s) optionally, then merge
directly to e-mail. e.g. if you have a field called includepage2 which is
"Y" if you want page 2, you might be able to use

{ IF "{ MERGEFIELD includepage2 }" = "Y" "put a page break in here with all
the other stuff you want, including fields" "" }

All the {} need to be the special field braces that you can insert using
ctrl-F9.

If you want to try this approach, I'd start by doing some very simple
feasibility tests on the machine you intend to use for the merge.

Otherwise, you can consider using VBA and a combination of two Doug Robbins
techniques, which you should find here:
http://www.gmayor.com/individual_merge_letters.htm
http://word.mvps.org/FAQs/MailMerge/MergeWithAttachments.htm

See the "Individual Merge Letters" item on fellow MVP Graham Mayor's website
at:

http://www.gmayor.com/individual_merge_letters.htm

If you are using Word XP or later, the "Add-in to Merge Letters to Separate
Files" that I have written and that can be downloaded from that site will
allow you to create each letter as a separate file with a filename taken
from a field in the data source with a minimum of fuss.

And then to email them out, see the article "Mail Merge to E-mail with
Attachments" at

http://word.mvps.org/FAQs/MailMerge/MergeWithAttachments.htm