Unable to copy content of an RTF file with it's formatting to a PDF file

I have an RTF file, trying to convert it to a PDF file. When I use following code, I get malformed PDF

Document rtfDoc = new Document(rtf);
DocumentBuilder builder = new DocumentBuilder(rtfDoc);
Document pdfDoc = rtfDoc.deepClone();

ImportFormatOptions options = new ImportFormatOptions();
options.setSmartStyleBehavior(false);

builder.insertDocument(pdfDoc, ImportFormatMode.*KEEP_SOURCE_FORMATTING*);
pdfDoc.save(pdf);
// and when I use the following code, I get a perfect PDF however, I have an extra blank pdf page.
Document invoicePdf = new Document();
// Open an existing document B
Document invoiceRtf = new Document(rtf);
// Add document B to the and of document A, preserving document B formatting

invoicePdf.appendDocument(invoiceRtf, ImportFormatMode.*KEEP_SOURCE_FORMATTING*);
// Save the output as PDF
invoicePdf.save(pdf, SaveFormat.*PDF*);

Please advice? Thanks

@quickfee Could you please attach your problematic documents and output here for testing? We will check the issue and provide you more information.