import ch.codeblock.qrinvoice.FontFamily;
import ch.codeblock.qrinvoice.OutputFormat;
import ch.codeblock.qrinvoice.PageSize;
import ch.codeblock.qrinvoice.QrInvoicePaymentPartReceiptCreator;
import ch.codeblock.qrinvoice.model.QrInvoice;
import ch.codeblock.qrinvoice.model.builder.QrInvoiceBuilder;

import java.util.Locale;

// ...

final QrInvoice qrInvoice = // create using QrInvoiceBuilder;

final PaymentPartReceipt paymentPartReceipt = QrInvoicePaymentPartReceiptCreator
    .create()
    .qrInvoice(qrInvoice)
    .outputFormat(OutputFormat.PDF)
    .pageSize(PageSize.DIN_LANG)
    .fontFamily(FontFamily.HELVETICA)
    .locale(Locale.GERMAN)
    .createPaymentPartReceipt();

// the resulting byte array contains the Swiss QR Code as PDF
final byte[] paymentPartReceiptPdf = paymentPartReceipt.getData();

// meta data for the chosen OutputFormat for convenience
final String mimeType = paymentPartReceipt.getOutputFormat().getMimeType();
final String fileExtension = paymentPartReceipt.getOutputFormat().getFileExtension();