If this is the same company which is licensing its software under a dual GPL-and-proprietary model, I think it probably makes the most sense for your company to simply license the manual under the GPL. This means that your company is the only one which can distribute *printed* copies of the manual without attaching a CD, diskette, or offer to provide source code. Some people will probably be willing to pay for the professionally printed copies. :-)
Note that, in the UK at least, adding a "free" CD jacks up the cost of a printed manual/book significantly. Given that a typical O'Reilly sells for between £20 and £40, adding a CD will also add about £5 tax to the price (books are VAT-free, adding a CD makes the *entire* *package* liable to 17.5% tax).
Cheers, Wol -- Anthony W. Youngman - anthony@thewolery.demon.co.uk