Attachment symbol is not coming in Documents

Dear all ;

I have created one document type SLD with Object type VBAP ie Sales Document item,and vendor Master record with LFA1 but the Problem is that there is no attachment symbol coming as it is coming for Purchase Order and RFQ .in sales order GO to item-- Additional .it is becoming Gray .

Thanking you;

Regardas;

Joydeep Mukherjee