Java PDFStamper 是一個用于處理 PDF 文檔的庫，但它已經被廢棄，現在推薦使用 iText 或 Apache PDFBox 等其他庫。這里我將為您提供一些關于使用 iText 庫的建議來解決常見問題。

1. 添加 iText 依賴項：

   對于 Maven 項目，請在 pom.xml 文件中添加以下依賴項：

對于 Gradle 項目，請在 build.gradle 文件中添加以下依賴項：

implementation 'com.itextpdf:itext7-core:7.1.16'

2. 合并 PDF 文件：

   import com.itextpdf.kernel.pdf.*;
   
   public void mergePdfFiles(List<String> inputFiles, String outputFile) {
       PdfWriter writer = new PdfWriter(outputFile);
       PdfDocument pdfDocument = new PdfDocument(writer);
       
       for (String inputFile : inputFiles) {
           PdfReader reader = new PdfReader(inputFile);
           PdfDocument sourceDocument = new PdfDocument(reader);
           sourceDocument.copyPagesTo(1, sourceDocument.getNumberOfPages(), pdfDocument);
           sourceDocument.close();
       }
       
       pdfDocument.close();
   }
   

3. 分割 PDF 文件：

   import com.itextpdf.kernel.pdf.*;
   
   public void splitPdfFile(String inputFile, String outputPath, int startPage, int endPage) {
       PdfReader reader = new PdfReader(inputFile);
       PdfDocument pdfDocument = new PdfDocument(reader);
       int numberOfPages = pdfDocument.getNumberOfPages();
       
       for (int i = startPage; i <= endPage && i <= numberOfPages; i++) {
           PdfWriter writer = new PdfWriter(outputPath + "/page_" + i + ".pdf");
           PdfDocument splitDocument = new PdfDocument(writer);
           pdfDocument.copyPagesTo(i, i, splitDocument);
           splitDocument.close();
       }
       
       pdfDocument.close();
   }
   

4. 添加水印：

   import com.itextpdf.kernel.pdf.*;
   import com.itextpdf.layout.Document;
   import com.itextpdf.layout.element.Paragraph;
   import com.itextpdf.layout.property.TextAlignment;
   
   public void addWatermark(String inputFile, String outputFile, String watermarkText) {
       PdfReader reader = new PdfReader(inputFile);
       PdfWriter writer = new PdfWriter(outputFile);
       PdfDocument pdfDocument = new PdfDocument(reader, writer);
       Document document = new Document(pdfDocument);
       
       for (int i = 1; i <= pdfDocument.getNumberOfPages(); i++) {
           Paragraph watermark = new Paragraph(watermarkText)
                   .setFontSize(48)
                   .setFontColor(ColorConstants.RED)
                   .setTextAlignment(TextAlignment.CENTER);
           document.showTextAligned(watermark, 297.5f, 421, i, TextAlignment.CENTER, VerticalAlignment.MIDDLE, 45);
       }
       
       document.close();
   }
   

5. 添加頁眉和頁腳：

   import com.itextpdf.kernel.pdf.*;
   import com.itextpdf.layout.Document;
   import com.itextpdf.layout.element.Paragraph;
   import com.itextpdf.layout.property.TextAlignment;
   
   public void addHeaderAndFooter(String inputFile, String outputFile, String headerText, String footerText) {
       PdfReader reader = new PdfReader(inputFile);
       PdfWriter writer = new PdfWriter(outputFile);
       PdfDocument pdfDocument = new PdfDocument(reader, writer);
       Document document = new Document(pdfDocument);
       
       for (int i = 1; i <= pdfDocument.getNumberOfPages(); i++) {
           // Add header
           Paragraph header = new Paragraph(headerText)
                   .setFontSize(12)
                   .setTextAlignment(TextAlignment.CENTER);
           document.showTextAligned(header, 297.5f, 806, i, TextAlignment.CENTER, VerticalAlignment.MIDDLE, 0);
           
           // Add footer
           Paragraph footer = new Paragraph(footerText + " | Page " + i)
                   .setFontSize(12)
                   .setTextAlignment(TextAlignment.CENTER);
           document.showTextAligned(footer, 297.5f, 55, i, TextAlignment.CENTER, VerticalAlignment.MIDDLE, 0);
       }
       
       document.close();
   }
   

這些示例應該可以幫助您解決使用 Java PDFStamper 時遇到的常見問題。如果您需要更多功能，請查看 iText 官方文檔：https://itextpdf.com/en/resources/documentation