Page body holds the central information of a page in most documents. This paper addresses the problem of automatically detecting page body area in digital books or journals. A novel method based on font expansion and header and footer elimination is detailed. This method extracts body text font (BFont) and headers and footers from a document first, and then draws two page body bounding boxes for each page, one by analyzing the distribution of BFont in pages and the other by removing headers and footers from pages. Finally, the two bounding boxes are combined to obtain the resultant page body bounding box. The test results demonstrate very high recognition rate: up to 99.49% in precision.