Doc export does not export the complete report, it just exports the snapshot which is visible in the window.
On my screen there is more data that I can see when I scroll right but when I try to export it as Doc file only the portion visible on the screen without scroll gets exported in the DOC file.
DOC has a fixed layout size. Even if you're using "auto" layout, the size of a page within the DOC output won't change. You'll have to set the masterpage size to change the size of the page in the DOC output. Hope this helps.