NoClassDefFoundError while integrating pdfbox jar file with siebel

Question

I'm using pdfbox-app-2.0.25.jar file for pdf generation and it is working fine in eclipse but while integrating it to Siebel, getting error

Error invoking service 'BTFLY B2B FTPV CAF Generation Service', method 'UserNameDesignation.doInvokeMethod' at step 'PDF Generation - FTPV'.(SBL-BPR-00162)--Class name incorrect or does not extend SiebelBusinessService : airtel/in/b2bcaf/FirstTimePhysicalVerification-- JVM Exception:java.lang.NoClassDefFoundError: org/apache/pdfbox/pdmodel/font/PDFont(SBL-EAI-05010)

I had compiled all my jar file into JAVASE-1.6 and added required class paths.

Here is the list of libraries imported in my class

import com.siebel.data.SiebelPropertySet;
import com.siebel.eai.SiebelBusinessService;
import com.siebel.eai.SiebelBusinessServiceException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.io.File;
import java.util.Date;
import java.util.HashMap;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.apache.pdfbox.pdmodel.PDDocument;   
import org.apache.pdfbox.pdmodel.PDPage;   
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.PDPageContentStream.AppendMode;
import org.apache.pdfbox.pdmodel.font.PDType1Font;