public static  void main(String[] args) throws Exception 
{
        if( args.length != 2 )
        {
            usage();
        }
        else
        {
            PDDocument document = null;
            try
            {
                document = PDDocument.load( args[0] );
                if( document.isEncrypted() )
                {
                    System.err.println( "Error: Encrypted documents are not supported for this example." );
                    System.exit( 1 );
                }
                List allPages = document.getDocumentCatalog().getAllPages();
                for( int i=0; i< allPages.size(); i++ )
                {
                    PDPage page = (PDPage)allPages.get( i );
                    PDFStreamParser parser = new PDFStreamParser(page.getContents());
                    parser.parse();
                    List tokens = parser.getTokens();
                    List newTokens = new ArrayList();
                    for( int j=0; j< tokens.size(); j++)
                    {
                        Object token = tokens.get( j );
                        if( token instanceof PDFOperator )
                        {
                            PDFOperator op = (PDFOperator)token;
                            if( op.getOperation().equals( "TJ") || op.getOperation().equals( "Tj" ))
                            {
                                //remove the one argument to this operator
                                newTokens.remove( newTokens.size() -1 );
                                continue;
                            }
                        }
                        newTokens.add( token );
                    }
                    PDStream newContents = new PDStream( document );
                    ContentStreamWriter writer = new ContentStreamWriter( newContents.createOutputStream() );
                    writer.writeTokens( newTokens );
                    newContents.addCompression();
                    page.setContents( newContents );
                }
                document.save( args[1] );
            }
            finally
            {
                if( document != null )
                {
                    document.close();
                }
            }
        }
}

This will remove all text from a PDF document.