public static void fitTableToPageWidth(Table table) {
    //Get the page settings from the section where the table occurs, as each section can have different page settings.
        Section section = (Section) table.getAncestor(NodeType.SECTION);
    //First run simply gets the table size (the widest row). This is used to calculate the ratio below instead of just each row length

//as the last cell in one row could be shorter than the last cell in the other row. This will preserve these different sizes when fitting.
        double tableWidth = 0;
        for (Row row : table.getRows()) {
            double rowWidth = 0;

            for (Cell cell : row.getCells()) {
                rowWidth += cell.getCellFormat().getWidth();
                cell.getCellFormat().setFitText(true);
            }
            //If this row is larger than previous set this width as the longest row.
            if (rowWidth > tableWidth)
            {
                tableWidth = rowWidth;
            }
        }
    //Calculate the width of the page
        double pageWidth = section.getPageSetup().getPageWidth() - (section.getPageSetup().getLeftMargin() + section.getPageSetup().getRightMargin());
    //In the second run set each cell in the row proportionally to the width of the page
        for(Row row : table.getRows()) {
            for(Cell cell : row.getCells())
            {
                //Calculate the ratio of each cell to the row width and then translate this ratio to the page width.
                double cellRatio = cell.getCellFormat().getWidth() / tableWidth;
                cell.getCellFormat().setWidth(cellRatio * pageWidth);
            }
        }
    }

原文地址：https://forum.aspose.com/t/autofit-tables-to-page-width-for-pdf/62893/2