Add Page Numbers to PDF Documents in Java Application

In our daily work, adding page numbers to a PDF document is important since it makes the document reading, retrieval and management easier. This article will introduce a simple and free way to add page numbers to an existing PDF document at the footer space by using Free Spire.PDF for Java. You can determine where to insert page numbers according to your own requirement.

Installation
Method 1: Download the Free Spire.PDF for Java and unzip it.Then add the Spire.Pdf.jar file to your project as dependency.

Method 2: You can also add the jar dependency to maven project by adding the following configurations to the pom.xml.

<repositories>
        <repository>
            <id>com.e-iceblue</id>
            <name>e-iceblue</name>
            <url>http://repo.e-iceblue.com/nexus/content/groups/public/</url>
        </repository>
</repositories>
<dependencies>
    <dependency>
        <groupId>e-iceblue</groupId>
        <artifactId>spire.pdf.free</artifactId>
        <version>2.6.3</version>
    </dependency>
</dependencies>

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Adding page numbers:

import com.spire.pdf.PdfDocument;
import com.spire.pdf.automaticfields.PdfCompositeField;
import com.spire.pdf.automaticfields.PdfPageCountField;
import com.spire.pdf.automaticfields.PdfPageNumberField;
import com.spire.pdf.graphics.*;

import java.awt.*;
import java.awt.geom.Dimension2D;
import java.awt.geom.Rectangle2D;

public class AddPageNumbers {

    public static void main(String[] args) {

        //load a PDF document
        PdfDocument doc = new PdfDocument();
        doc.loadFromFile("input.pdf");

        //create a true type font
        PdfTrueTypeFont font = new PdfTrueTypeFont(new Font("Times New Roman", Font.PLAIN, 12));

        //get the page size
        Dimension2D pageSize = doc.getPages().get(0).getSize();

        //declare a float variable
        float y = (float) pageSize.getHeight() - 72;

        //loop through the pages
        for (int i = 0; i < doc.getPages().getCount(); i++) {

            //initialize PdfPageNumberField instance
            PdfPageNumberField number = new PdfPageNumberField();

            //initialize PdfPageCountField instance
            PdfPageCountField count = new PdfPageCountField();

            //create PdfCompositeField instance
            PdfCompositeField compositeField = new PdfCompositeField(font, PdfBrushes.getBlack(), "Page {0} of {1}", number, count);

            //set the text alignment within the composite field
            compositeField.setStringFormat(new PdfStringFormat(PdfTextAlignment.Right, PdfVerticalAlignment.Top));

            //get the text size
            Dimension2D textSize = font.measureString(compositeField.getText());

            //set the position and size of composite field
            compositeField.setBounds(new Rectangle2D.Float((float) pageSize.getWidth() - (float) textSize.getWidth() - 80, y, (float) textSize.getWidth(), (float) textSize.getHeight()));

            //draw composite filed on PDF page
            compositeField.draw(doc.getPages().get(i).getCanvas());
        }

        //save to another file
        doc.saveToFile("PageNumbers.pdf");
    }
}

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原文链接：Add Page Numbers to PDF Documents in Java Application