The largest Word document I've created was 1,267 pages compiled from multiple sources and formats. It used all 9 levels of numbered headings and contained ~350 graphics and over 400 tables. The final file size of 28MB was achieved by using a Photoshop script to reduce color images to 128 color gifs at exactly 110 dpi. Scrolling response was a bit slow in print view, but otherwise it was fine. After initial authoring, 6 others edited the content with no problems.