PDFBox:如何正确地将注释从一个pdf复制到另一个pdf

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDAnnotation;
import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class PDFBoxExample {
    public static void main(String[] args) {
        try {
            // Load source and target PDF documents
            PDDocument sourceDocument = PDDocument.load(new File("source.pdf"));
            PDDocument targetDocument = PDDocument.load(new File("target.pdf"));

            // Get annotations from source PDF
            List<PDAnnotation> annotations = new ArrayList<>();
            for (PDPage page : sourceDocument.getPages()) {
                annotations.addAll(page.getAnnotations());
            }

            // Add annotations to target PDF
            int pageIndex = 0;
            for (PDPage page : targetDocument.getPages()) {
                List<PDAnnotation> targetAnnotations = page.getAnnotations();
                targetAnnotations.addAll(annotations);
                page.setAnnotations(targetAnnotations);
                targetDocument.getPages().set(pageIndex, page);
                pageIndex++;
            }

            // Save the modified target PDF
            targetDocument.save("target_with_comments.pdf");

            // Close the documents
            sourceDocument.close();
            targetDocument.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}