I am trying to use iText’s PdfReader to check if a given PDF file is password protected or not, but am getting this exception: Exception in thread “Main Thread” java.lang.NoClassDefFoundError:org/bouncycastle/asn1/ASN1OctetString But when testing the same code against a non-password protected file it runs fine. Here is the complete code: Answer Use Apache PDFBox – Java PDF Library from here:Sample Code: