PDF的宽度取决于您的Excel打印设置，默认情况下，它将设置为A4纵向，因此导出PDF将把一半数据留到下一行;如果将纸张大小设置为A3横向，然后导出为PDF，则将显示正确的格式。

我经历过同样的问题，所以我做了：
1.对于excel文件工作表，我设置了以下内容

xlWorkbook = xlApps.Workbooks.Add(missing);
        xlWorkSheet = (Excel.Worksheet)xlWorkbook.Worksheets.get_Item(1);
        xlApps.ActiveWindow.View = Excel.XlWindowView.xlPageLayoutView; //pagelayout view
        xlWorkSheet.PageSetup.PaperSize = Excel.XlPaperSize.xlPaperA4; //set paper to A4
        xlWorkSheet.PageSetup.Orientation = Excel.XlPageOrientation.xlPortrait; //set to portrait

        //margins 'Narrow'   
        xlWorkSheet.PageSetup.LeftMargin = 0.65; //55
        xlWorkSheet.PageSetup.RightMargin = 0.25;
        xlWorkSheet.PageSetup.BottomMargin = 0.75;
        xlWorkSheet.PageSetup.TopMargin = 0.75; //60
        xlWorkSheet.PageSetup.HeaderMargin = 0;

1.转换我的excel文件和规模的大小。（只是改变120，以适应您的文件）

//here is the scaling
        Worksheet xlmsheet = excelWorkBook.Sheets[1];
        xlmsheet.PageSetup.Zoom = 120; 
         // Save it in the target format.
        if (excelWorkBook != null)
            excelWorkBook.ExportAsFixedFormat(XlFixedFormatType.xlTypePDF, paramExportFilePath, XlFixedFormatQuality.xlQualityStandard, true,
                true, Type.Missing, Type.Missing, false, paramMissing);

为什么不直接使用“适合页面宽度”和“适合页面高度”

xlWorkSheet.PageSetup.Zoom = False
    xlWorkSheet.PageSetup.FitToPagesWide = 1
    xlWorkSheet.PageSetup.FitToPagesTall = 1