I use both Pagemaker and MS Word and there are some things Word will do that Pagemaker won't do and vice versa.
PM, being a page layout program for professionals is much more difficult to use than MSW, but does allow the most accurate placement of graphics and design features. Both can export or print to PDF through Distiller of Adobe Writer. Distiller is best and can export from PM.
There's no reason why you cannot type your native text into MSW and import into PM when you have each chapter finished.
Give some thought to whether you will create a book style ie, one page per view, or an A4 or Letter layout which requires scrolling.