PDF text replace not working

问题

I'm trying to replace text in PDF using iTextSharp dll but its not working in all cases. PDF document doesn't have acro fields.

If the text which I need to replace is bigger than original text its not printing all characters. Finding some special characters is also not working.

I have tried this code

using (PdfReader reader = new PdfReader(sourceFileName))
{
    for (int i = 1; i <= reader.NumberOfPages; i++)
    {
        byte[] contentBytes = reader.GetPageContent(i);
        string contentString = PdfEncodings.ConvertToString(contentBytes, PdfObject.TEXT_PDFDOCENCODING);
        contentString = contentString.Replace("SOMETEXT", "NEWBIGGERTEXT");                 
        reader.SetPageContent(i, PdfEncodings.ConvertToBytes(contentString, PdfObject.TEXT_PDFDOCENCODING));
    }
    new PdfStamper(reader, new FileStream(newFileName, FileMode.Create, FileAccess.Write)).Close();
}

Please let me know how this can be achieved.

来源：https://stackoverflow.com/questions/41726826/pdf-text-replace-not-working