转换功能是通过调用安装了转换XPS和PDF的AddIn的Office2007对象模型完成的. 代码支持Office 2007支持的一切文件格式:
 

Office 2007组件	扩展名
Word	DOC, DOCX, DOCM, DOTX, DOTM, DOT, TXT, RTP, RTF
Excel	XLS, XLSX, XLSM, XML
PowerPoint	PPT, PPTX, PPTM, POTX, PPSX, PPSM, POTM

添加对三个组件的引用：

这里使用一个枚举类型来来决定生成文件的类型,包括：



其实可以使用个方法来实现这个功能，这里Word和Excel我使用了ExportAsFixedFormat，PowerPoint使用了SaveAs，对于Word和PowerPoint效果是一样的。只是SaveAs支持的格式更多, 但我发现似乎Excel不支持SaveAs.

Word转换代码:

        private bool Convert(string sourcePath, string targetPath, Word.WdExportFormat exportFormat)
        {
            bool result;
            object paramMissing = Type.Missing;
            Word.ApplicationClass wordApplication = new Word.ApplicationClass();
            Word.Document wordDocument = null;
            try
            {
                object paramSourceDocPath = sourcePath;
                string paramExportFilePath = targetPath;

                Word.WdExportFormat paramExportFormat = exportFormat;
                bool paramOpenAfterExport = false;
                Word.WdExportOptimizeFor paramExportOptimizeFor =
                    Word.WdExportOptimizeFor.wdExportOptimizeForPrint;
                Word.WdExportRange paramExportRange = Word.WdExportRange.wdExportAllDocument;
                int paramStartPage = 0;
                int paramEndPage = 0;
                Word.WdExportItem paramExportItem = Word.WdExportItem.wdExportDocumentContent;
                bool paramIncludeDocProps = true;
                bool paramKeepIRM = true;
                Word.WdExportCreateBookmarks paramCreateBookmarks =
                    Word.WdExportCreateBookmarks.wdExportCreateWordBookmarks;
                bool paramDocStructureTags = true;
                bool paramBitmapMissingFonts = true;
                bool paramUseISO19005_1 = false;

                wordDocument = wordApplication.Documents.Open(
                    ref paramSourceDocPath, ref paramMissing, ref paramMissing,
                    ref paramMissing, ref paramMissing, ref paramMissing,
                    ref paramMissing, ref paramMissing, ref paramMissing,
                    ref paramMissing, ref paramMissing, ref paramMissing,
                    ref paramMissing, ref paramMissing, ref paramMissing,
                    ref paramMissing);

                if (wordDocument != null)
                    wordDocument.ExportAsFixedFormat(paramExportFilePath,
                        paramExportFormat, paramOpenAfterExport,
                        paramExportOptimizeFor, paramExportRange, paramStartPage,
                        paramEndPage, paramExportItem, paramIncludeDocProps,
                        paramKeepIRM, paramCreateBookmarks, paramDocStructureTags,
                        paramBitmapMissingFonts, paramUseISO19005_1,
                        ref paramMissing);
                result = true;
            }
            finally
            {
                if (wordDocument != null)
                {
                    wordDocument.Close(ref paramMissing, ref paramMissing, ref paramMissing);
                    wordDocument = null;
                }
                if (wordApplication != null)
                {
                    wordApplication.Quit(ref paramMissing, ref paramMissing, ref paramMissing);
                    wordApplication = null;
                }
                GC.Collect();
                GC.WaitForPendingFinalizers();
                GC.Collect();
                GC.WaitForPendingFinalizers();
            }
            return result;
        }

private bool Convert(string sourcePath, string targetPath, XlFixedFormatType targetType)
        {
            bool result;
            object missing = Type.Missing;
            ApplicationClass application = null;
            Workbook workBook = null;
            try
            {
                application = new ApplicationClass();
                object target = targetPath;
                object type = targetType;
                workBook = application.Workbooks.Open(sourcePath, missing, missing, missing, missing, missing,
                    missing, missing, missing, missing, missing, missing, missing, missing, missing);                workBook.ExportAsFixedFormat(targetType, target, XlFixedFormatQuality.xlQualityStandard, true, false, missing, missing, missing, missing);
                result = true;
            }
            catch
            {
                result = false;
            }
            finally
            {
                if (workBook != null)
                {
                    workBook.Close(true, missing, missing);
                    workBook = null;
                }
                if (application != null)
                {
                    application.Quit();
                    application = null;
                }
                GC.Collect();
                GC.WaitForPendingFinalizers();
                GC.Collect();
                GC.WaitForPendingFinalizers();
            }
            return result;
        }

PowerPoint转换代码：

       private bool Convert(string sourcePath, string targetPath, PpSaveAsFileType targetFileType)
        {
            bool result;
            object missing = Type.Missing;
            ApplicationClass application = null;
            Presentation persentation = null;
            try
            {
                application = new ApplicationClass();
                persentation = application.Presentations.Open(sourcePath, MsoTriState.msoTrue, MsoTriState.msoFalse, MsoTriState.msoFalse);
                persentation.SaveAs(targetPath, targetFileType, Microsoft.Office.Core.MsoTriState.msoTrue);

                result = true;
            }
            catch
            {
                result = false;
            }
            finally
            {
                if (persentation != null)
                {
                    persentation.Close();
                    persentation = null;
                }
                if (application != null)
                {
                    application.Quit();
                    application = null;
                }
                GC.Collect();
                GC.WaitForPendingFinalizers();
                GC.Collect();
                GC.WaitForPendingFinalizers();
            }
            return result;
        }

感谢同事Hong的协助,把这部分功能实现，现在share给大家，希望为需要的朋友节省时间.
另外浏览xps文件有一个不错的小工具XPS Viewer EP.