Hi,
Well, 150 pages isn't all that bad - there's a fair chance WORD coud still do it (though with larger files word tends to crash. if you only have text and not too many hyperlinks it can work).
That being said - the pros I know use Adobe FrameMaker. You can chek it out on Adobe's website (http://www.adobe.com/products/framemaker/)
This is not coming to endorse Adobe's product (I find their Acrobat reader to be a real virus and much prefer Foxit reader). However - from my shallow and brief knowledge of FrameMaker, there is no comparison with Word. It's like Photoshop vs. MS-paint. Framemaker is a professional editing software with many more options for serious editing, publishing and printing. I think most people who work with it are happy to do so. The 2 downsides would be: 1. price 2. learning curve.
hope that helps.