I've been presented with 20 Word files (over 21Mb) where the author has
inserted screenshots using alt + prt scn and ctrl + v. I estimate that
converting the graphics (24bit) to 8 colour (6 bit?)gif's and reducing the
"bpi" will cut the document sizes down by 60+%.

So far the only method I have identified is to save each doc as an html
file, batch convert the image files to gif , perform a find and replace of
*.jpg to *.gif on the html doc and the index file , open the html doc and
save as a Word doc. The files are heavily hyperlinked and bookmarked and
indexed and I don't want to lose these features.

Have I identified the only solution or is there a better way? - my current
method is far quicker than a cut , reformat and paste back image by image.