using Spire.Doc;
using Spire.Xls;
using Spire.Pdf;
using System.IO;

 //聲明PdfDocument對象數(shù)組
   PdfDocument[] documents = new PdfDocument[4];
   using (MemoryStream ms1 = new MemoryStream())
   {
    //加載doc文檔
    Document doc = new Document(@"C:\Users\Administrator\Desktop\sample.doc", Spire.Doc.FileFormat.Doc);
    //轉(zhuǎn)換PDF，并以流的形式保存
    doc.SaveToStream(ms1, Spire.Doc.FileFormat.PDF);
    //加載PDF流文件為PdfDocument對象數(shù)組的第一個元素
    documents[0] = new PdfDocument(ms1);
   }
   using (MemoryStream ms2 = new MemoryStream())
   {
    //加載docx文檔 
    Document docx = new Document(@"C:\Users\Administrator\Desktop\test.docx", Spire.Doc.FileFormat.Docx2010);

    //轉(zhuǎn)換PDF，并以流的形式保存 
    docx.SaveToStream(ms2, Spire.Doc.FileFormat.PDF);
    //加載PDF流文件為PdfDocument對象數(shù)組的第二個元素
    documents[1] = new PdfDocument(ms2);
   }

   using (MemoryStream ms3 = new MemoryStream())
   {
    //加載xlsx文檔
    Workbook workbook = new Workbook();
    workbook.LoadFromFile(@"C:\Users\Administrator\Desktop\Sample.xlsx", ExcelVersion.Version97to2003);
    //轉(zhuǎn)換PDF，并以流的形式保存
    workbook.SaveToStream(ms3, Spire.Xls.FileFormat.PDF);
    //加載PDF流文件為PdfDocument對象數(shù)組的第三個元素
    documents[2] = new PdfDocument(ms3);
   }

   //加載pdf文檔，作為PdfDocument對象數(shù)組的第四個元素
   documents[3] = new PdfDocument(@"C:\Users\Administrator\Desktop\sample.pdf");
   //將前三個文檔合并到第四個文檔，并另存為新的PDF文檔
   for (int i = 2; i > -1; i--)
   {
    documents[3].AppendPage(documents[i]);
   }

   documents[3].SaveToFile("Result.pdf");