Yep, thats what I do with all my 'book/instruction' pdfs.
The Savage Worlds ones I do a colour cover, but the interior is all B&W.
The WWG/SE ones were completely B&W but still used a noticable amount of ink.
The Watch Tower instructions actually made my computer hang when I tried printing the whole instruction document. I had to reboot the computer and print off 5 pages at a time. First time this has happened!
I know the Instructions aren't 100+ pages like the SW books, but Harbourmaster had about 60+ pages, Watch Tower about 25 pages. Mayhem had a load, Mars Station had a load.
The instructions are excellent resources for assembly and figuring out what to do first and what needs to be printed for a certain item, but the filesize due to all the backgrounds could be reduced methinks, IMHO of course
Just a suggestion.