Converting multiple pages of a PDF to grayscale.

It should be possible to use a script to extract those pages as a new file (in fact, I've already developed a paid-for tool that does just that: http://try67.blogspot.com/2011/04/acrobat-extract-non-sequential-pages.html), convert them to gray-scale (since you could now use the option to process all pages on this new file) and then use another script to import them back into the original file, replacing the current pages with the new ones.

If you're interested I could develop the full tool for you that does that, for a fee. You can contact me privately via [try6767 at gmail.com] to discuss it further.

Although we certainly understand your need, there is currently no simple way of doing this directly in Acrobat.

I would recommend that you recommend an ability to specify multiple pages and ranges of pages in this (and perhaps) other Acrobat dialogs at the following website that is monitored by Acrobat Engineering management: https://acrobat.uservoice.com/forums/590923-acrobat-for-windows-and-mac 

              - Dov