To modify outgoing invoices modify the following file: "/includes/pdfconfig.php"
You can modify this file to your hearts content to get the look & feel you require.
just comment out the following lines:
$pdf->Cell(155,7,$_LANG["invoicescredit"].":",1,0,'R','1');
$pdf->Cell(25,7,$currencysymbol.$credit,1,0,'R','1');
$pdf->Ln();
**note: The above lines might might differ in their numbers as I have heavily modified the original supplied file.
you would also have to ensure that no "credit" is applied to the invoice via WHMCS or add in another line, (where you commented out the above code), to add the "credit" back to the "Total" something like:
$total = $total + $credit;
hope this helps
graham