First time I used iText API - http://www.itextpdf.com/itext.php
After I scan the document I save it as pdf like this:
public static bool SavePDFAs(string picname, IntPtr bminfo, IntPtr pixdat)
{
SaveFileDialog sd = new SaveFileDialog();
sd.FileName = picname;
sd.Title = "Save file as...";
sd.Filter = "PDF file (*.pdf)|*.pdf";
sd.FilterIndex = 1;
if (sd.ShowDialog() != DialogResult.OK)
return false;
Document doc = new Document(PageSize.A4);
try
{
FileStream PDFfs = new FileStream(sd.FileName, FileMode.Create);
PdfWriter.GetInstance(doc, PDFfs);
doc.Open();
Bitmap bmp = BitmapFromDIB(bminfo, pixdat);
bmp.SetResolution(300, 300);
byte[] imageBytes;
using (MemoryStream ms = new MemoryStream())
{
// Convert Image to byte[]
bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
imageBytes = ms.ToArray();
}
bmp.Dispose();
iTextSharp.text.Image png = iTextSharp.text.Image.GetInstance(imageBytes);
png.ScalePercent(24f);
png.SetAbsolutePosition(0, 0);
doc.Add(png);
}
catch (DocumentException dex)
{
MessageBox.Show(dex.Message);
}
catch (IOException ioex)
{
MessageBox.Show(ioex.Message);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
return false;
}
finally
{
doc.Close();
}
return true;
}
.
by Stephen G. Kochan
by Mark Dalrymple, Scott Knaster
by Dave Mark, Jeff LaMarche 
