How to rectify the error "The type or namespace name 'PdfWriter' could not be found (are you missing a using directive or an assembly reference?)"

i just tried a pdf document generation program.... using iTextsharp in asp.net using c#

in that the web page is successfully running on my local system...

whenever i tried to run on website i am getting error ... like

The type or namespace name 'PdfWriter' could not be found (are you missing a using directive or an assembly reference?)

for the following code

private static void DrawLine(PdfWriter writer, float x1, float y1, float x2, float y2, Color color)
{
       PdfContentByte contentByte = writer.DirectContent;

please help me to rectify the error....

thanks in advance...