The com.itextpdf.text.Anchor class in iText can be used to create an internal link or external link in a PDF document. To create an internal link we must format the anchor reference using the # + referenceName. On the other side the target anchor should be named using the same reference name excluding the # symbol.

To set the reference we use the setReference() method. To define the target anchor we can name the anchor using the setName() method.

package org.kodejava.itextpdf;

import com.itextpdf.text.Anchor;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.PdfWriter;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;

public class AnchorInternalDemo {
    public static void main(String[] args) {
        Document document = new Document();
        try {
            PdfWriter.getInstance(document, new FileOutputStream("AnchorInternal.pdf"));
            document.open();

            Anchor anchor = new Anchor("[Continue Here]");
            anchor.setReference("#targetLink");
            Paragraph para1 = new Paragraph("The quick brown fox jumps over the lazy dog. ");
            para1.add(anchor);
            document.add(para1);

            Anchor target = new Anchor("The quick onyx goblin jumps over the lazy dwarf.");
            anchor.setName("targetLink");
            Paragraph para2 = new Paragraph();
            para2.setSpacingBefore(150);
            para2.add(target);
            document.add(para2);

            document.close();
        } catch (DocumentException | FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            document.close();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.13.3</version>
</dependency>