pdf通过itext包增加水印

public static void main(String[] args) throws Exception { 
        PdfReader reader = new PdfReader(new FileInputStream(new File("E:/e1c84094314443dbba6c3f77ea907030.pdf")));//存在的文件
        PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(new File("E:/pdfWithWaterMark.pdf")));//输出文件
        int total = reader.getNumberOfPages() + 1;//pdf总页数
        PdfContentByte content;
        BaseFont base = BaseFont.createFont("C:/WINDOWS/Fonts/SIMSUN.TTC,1",BaseFont.IDENTITY_H, BaseFont.EMBEDDED);
        PdfGState gs = new PdfGState();
　　　　 int a=0,b=0,c=35; //a距左,b距下,c倾斜度
        for (int i = 1; i < total; i++) {
            content = stamper.getOverContent(i);// 在内容上方加水印
            // content = stamper.getUnderContent(i);//在内容下方加水印
            gs.setFillOpacity(0.4f);
            content.setGState(gs);// 透明度
            content.beginText();
            content.setColorFill(Color.LIGHT_GRAY);
            content.setFontAndSize(base, 30);
            content.setTextMatrix(70, 200);   
            content.showTextAligned(Element.ALIGN_CENTER, "测试水印", a, b, c);
            content.setColorFill(Color.BLACK);
            content.setFontAndSize(base, 8);
            content.endText();
        }
        stamper.close();
}            

content.showTextAligned(Element.ALIGN_CENTER, "测试水印", a, b, c);

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.4.5</version>
</dependency>