以下是一个使用不同的PDFont类型处理和操作PDF文档字体的示例代码：

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.font.PDType1Font;
import org.apache.pdfbox.pdmodel.font.PDType0Font;
import org.apache.pdfbox.pdmodel.font.PDTrueTypeFont;
import org.apache.pdfbox.pdmodel.font.PDType3Font;

import java.io.IOException;

public class PDFontExample {
    public static void main(String[] args) {
        try {
            // 创建一个新的PDF文档
            PDDocument document = new PDDocument();
            PDPage page = new PDPage();
            document.addPage(page);

            // 使用PDType1Font
            PDType1Font type1Font = PDType1Font.HELVETICA_BOLD;
            PDPageContentStream contentStream1 = new PDPageContentStream(document, page);
            contentStream1.setFont(type1Font, 12);
            contentStream1.beginText();
            contentStream1.newLineAtOffset(100, 700);
            contentStream1.showText("This is a Type 1 font example.");
            contentStream1.endText();
            contentStream1.close();

            // 使用PDType0Font
            PDType0Font type0Font = PDType0Font.load(document, PDFontExample.class.getResourceAsStream("/fonts/arialuni.ttf"));
            PDPageContentStream contentStream2 = new PDPageContentStream(document, page, PDPageContentStream.AppendMode.APPEND, true);
            contentStream2.setFont(type0Font, 12);
            contentStream2.beginText();
            contentStream2.newLineAtOffset(100, 680);
            contentStream2.showText("这是一个Type 0字体的示例。");
            contentStream2.endText();
            contentStream2.close();

            // 使用PDTrueTypeFont
            PDTrueTypeFont trueTypeFont = PDTrueTypeFont.load(document, PDFontExample.class.getResourceAsStream("/fonts/arial.ttf"));
            PDPageContentStream contentStream3 = new PDPageContentStream(document, page, PDPageContentStream.AppendMode.APPEND, true);
            contentStream3.setFont(trueTypeFont, 12);
            contentStream3.beginText();
            contentStream3.newLineAtOffset(100, 660);
            contentStream3.showText("This is a TrueType font example.");
            contentStream3.endText();
            contentStream3.close();

            // 使用PDType3Font
            PDType3Font type3Font = PDType3Font.load(document, PDFontExample.class.getResourceAsStream("/fonts/customfont.afm"));
            PDPageContentStream contentStream4 = new PDPageContentStream(document, page, PDPageContentStream.AppendMode.APPEND, true);
            contentStream4.setFont(type3Font, 12);
            contentStream4.beginText();
            contentStream4.newLineAtOffset(100, 640);
            contentStream4.showText("This is a Type 3 font example.");
            contentStream4.endText();
            contentStream4.close();

            // 保存PDF文档
            document.save("output.pdf");
            document.close();

            System.out.println("PDF文档已生成。");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

在上面的示例中，我们使用了不同的PDFont类型来处理和操作PDF文档中的字体。根据具体的需求，开发人员可以选择合适的字体类型来渲染文本。