import com.itextpdf.text.*;
import com.itextpdf.text.pdf.*;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class PDFUtil {

    /**
     *
     * @param pdfData
     * @param pageIndex
     * @param x
     * @param y
     * @param text
     * @return
     * @throws IOException
     * @throws DocumentException
     */
    public static byte[] pdfWriteText(byte[] pdfData, int pageIndex,
                                      int x, int y, String text, float textSize) throws IOException, DocumentException {

        PdfReader reader = new PdfReader(pdfData);
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        PdfStamper stamper = new PdfStamper(reader, baos);
        BaseFont baseFont = BaseFont.createFont("STSong-Light", "UniGB-UCS2-H", false);
        Font font = new Font(baseFont, textSize);
        pageIndex = handlerPageSize(reader.getNumberOfPages(), pageIndex);

        PdfContentByte over = stamper.getOverContent(pageIndex);
        ColumnText columnText = new ColumnText(over);
        // llx 和 urx  最小的值决定离左边的距离. lly 和 ury 最大的值决定离下边的距离
        //预留一些长度 防止越界被截掉
        columnText.setSimpleColumn(x, y, x + (text.length() * textSize) + 8, y + textSize + 8);
        Paragraph elements = new Paragraph(0, new Chunk(text));
        // 设置字体，如果不设置添加的中文将无法显示
        elements.setFont(font);
        columnText.addElement(elements);
        columnText.go();
        stamper.close();

        return baos.toByteArray();
    }


    /**
     * 将 index 转为从1开始，防止越界(通过循环的方式解决)，并且解析负数
     * @param total
     * @param index 0 表示页数不存在
     * @return
     */
    public static int handlerPageSize(int total, int index) {
        if(total < 1) {
            return 0;
        } else if(index == 0) {
            return 1;
        } else if(index < 0) {
            index = index + total + 1;
        }
        int r = index % total;
        return r == 0 ? total : r;
    }

    /**
     * 多区间
     * @param pdfData
     * @param pages int [] size must is 2 else ignore
     * @return
     * @throws IOException
     * @throws DocumentException
     */
    public static byte[] splitPDFFile(byte[] pdfData, int [][] pages) throws IOException, DocumentException {
        PdfReader reader = new PdfReader(pdfData);
        int total = reader.getNumberOfPages();

        Document document = new Document(reader.getPageSize(1));
        ByteArrayOutputStream b = new ByteArrayOutputStream();
        PdfCopy copy = new PdfCopy(document, b);
        document.open();
        for(int[] index : pages) {
            if(index == null || index.length != 2) {
                continue;
            }
            int start = handlerPageSize(total, index[0]);
            int end = handlerPageSize(total, index[1]);
            for(int i = start; i <= end; i++) {
                document.newPage();
                PdfImportedPage page = copy.getImportedPage(reader, i);
                copy.addPage(page);
            }
        }
        document.close();
        return b.toByteArray();
    }

    /**
     * 多零散页
     * @param pdfData
     * @param pages
     * @return
     * @throws IOException
     * @throws DocumentException
     */
    public static byte[] splitPDFFile(byte[] pdfData, int [] pages) throws IOException, DocumentException {
        PdfReader reader = new PdfReader(pdfData);
        int total = reader.getNumberOfPages();

        Document document = new Document(reader.getPageSize(1));
        ByteArrayOutputStream b = new ByteArrayOutputStream();
        PdfCopy copy = new PdfCopy(document, b);
        document.open();
        for(int index : pages) {
            document.newPage();
            PdfImportedPage page = copy.getImportedPage(reader, handlerPageSize(total, index));
            copy.addPage(page);
        }
        document.close();
        return b.toByteArray();
    }

    /**
     * 截取pdfFile的第from页至第end页(注意是一个闭区间)，组成一个新的文件
     * @param pdfData
     * @param from (从1开始) 负数表示从最后一页算起
     * @param end 负数表示从最后一页算起
     * @return
     * @throws IOException
     * @throws DocumentException
     */
    public static byte[] splitPDFFile(byte[] pdfData, int from, int end) throws IOException, DocumentException {
        PdfReader reader = new PdfReader(pdfData);
        int total = reader.getNumberOfPages();
        //保证从1开始，并且解析负数。
        from = handlerPageSize(total, from);
        end = handlerPageSize(total, end);

        Document document = new Document(reader.getPageSize(1));
        ByteArrayOutputStream b = new ByteArrayOutputStream();
        PdfCopy copy = new PdfCopy(document, b);
        document.open();
        for(int j = from; j <= end; j++) {
            document.newPage();
            PdfImportedPage page = copy.getImportedPage(reader, j);
            copy.addPage(page);
        }
        document.close();
        return b.toByteArray();
    }



}

<dependency>
            <groupId>com.itextpdf</groupId>
            <artifactId>itextpdf</artifactId>
            <version>5.5.13</version>
        </dependency>
        <dependency>
            <groupId>com.itextpdf</groupId>
            <artifactId>itext-asian</artifactId>
            <version>5.2.0</version>
        </dependency>