How Can i convert this smartform to pdf ?

DATA : ITAB_DATA LIKE ZPBYILDIZ_DE_04 OCCURS 0 WITH HEADER LINE.

DATA : ITAB_DATA_ST LIKE ITAB_DATA.

Note : itab_detail4 is internal table

         ZPBYILDIZ_DE_04 is structure

WHEN '&PRNT'.

     READ TABLE ITAB_DETAIL4 INDEX ls_selfield1-tabindex.

     LOOP AT ITAB_DETAIL4 INTO ITAB_DATA.

        MOVE-CORRESPONDING ITAB_DATA TO ITAB_DATA_ST.

         APPEND ITAB_DATA_ST TO ITAB_DATA.

     ENDLOOP.

CALL FUNCTION 'SSF_FUNCTION_MODULE_NAME'

         EXPORTING

           formname = 'ZP0834_SF05'

         IMPORTING

           FM_NAME  = FM_NAME.

       CALL FUNCTION FM_NAME

         TABLES

           ITAB_DATA = ITAB_DATA[].

WHEN '&PDF'.

..........(HEAR!  I calling pdf)