Filla a rich text field in a PDF file and then creates it's appearances.

FillRichTextField.java

package pdfjt.cookbook.forms;
/*
 * Copyright 2016 Datalogics, Inc.
 */
import com.adobe.fontengine.font.Font;
import com.adobe.internal.io.ByteReader;
import com.adobe.internal.io.InputStreamByteReader;
import com.adobe.pdfjt.pdf.document.PDFDocument;
import com.adobe.pdfjt.pdf.document.PDFOpenOptions;
import com.adobe.pdfjt.pdf.document.PDFSaveFullOptions;
import com.adobe.pdfjt.pdf.document.PDFText;
import com.adobe.pdfjt.pdf.graphics.font.PDFFont;
import com.adobe.pdfjt.pdf.interactive.forms.PDFFieldNode;
import com.adobe.pdfjt.pdf.interactive.forms.PDFInteractiveForm;
import com.adobe.pdfjt.services.ap.AppearanceService;
import com.adobe.pdfjt.services.ap.TextFormatterImpl;
import com.adobe.pdfjt.services.ap.extension.APExtensionOptions;
import com.adobe.pdfjt.services.ap.spi.APContext;
import com.adobe.pdfjt.services.ap.spi.APResources;
import com.adobe.pdfjt.services.rcg.impl.RichTextHandler;
import com.datalogics.pdf.document.DocumentHelper;

import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Scanner;

/**
 */
public class FillRichTextField {

    private static final String inputPDF_URL = "http://dev.datalogics.com/cookbook/forms/RichText.pdf";
    private static final String inputXML_URL = "http://dev.datalogics.com/cookbook/forms/RichText.xml";
    private static final String userAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.95 Safari/537.11";

    public static void main(final String... args) throws Exception {
	// First get the PDF file
	URLConnection connection = new URL(inputPDF_URL).openConnection();
        connection.setRequestProperty("User-Agent", userAgent);
        connection.connect();
        InputStream fis = connection.getInputStream();
        ByteReader byteReader = new InputStreamByteReader(fis);
        PDFDocument pdfDocument = PDFDocument.newInstance(byteReader, PDFOpenOptions.newInstance());
	// Then get the XML that represents the Rich Text
        connection = new URL(inputXML_URL).openConnection();
        connection.setRequestProperty("User-Agent", userAgent);
        connection.connect();
        fis = connection.getInputStream();
	Scanner scanner = new Scanner(fis, StandardCharsets.UTF_8.name());
        String xmlString = scanner.useDelimiter("\\A").next();
        scanner.close();
        // Now we can fill the /RV key of the field "richText1" with the XML string
	PDFInteractiveForm pdfInteractiveForm = pdfDocument.requireCatalog().getInteractiveForm();
        PDFFieldNode richTextField = pdfInteractiveForm.getChildren().getFieldFullyNamed("richText1");
        richTextField.setRichText(PDFText.createString(pdfDocument, xmlString));
        // Next we have to set the /V key with just the text portion of the XML otherwise Acrobat won't be able to edit the field.
        String rawValue = new RichTextHandler().getRawContent(xmlString);
        richTextField.setStringValue(rawValue);
        // Finally we can generate the appearance.
        APResources apResources = new APResources(
                                                        pdfDocument.getCosDocument().getOptions().getFontSet(),
                                                        pdfDocument.getCosDocument().getOptions().getDocLocale(),
                                                        new HashMap<Font, PDFFont>());
        APExtensionOptions apExtensionOptions = APExtensionOptions.newInstance();
        APContext apContext = new APContext(apResources, true, apExtensionOptions);
        AppearanceService.generateAppearances(pdfDocument, apContext, new TextFormatterImpl(pdfDocument));
        // Save and close the file.
        DocumentHelper.saveAndClose(pdfDocument, "RichText_Output.pdf", PDFSaveFullOptions.newInstance());
        System.out.println("Done!");
    }
}