I know its very late but might help someone. Here is the way to do it.
Create a class BGClass, implement PdfPCellEvent and enter following method.
@Override
public void cellLayout(PdfPCell arg0, Rectangle arg1, PdfContentByte[] arg2) {
try {
PdfContentByte pdfContentByte = arg2[PdfPTable.BACKGROUNDCANVAS];
Image bgImage = Image.getInstance("URL_TO_YOUR_IMAGE");
pdfContentByte.addImage(bgImage, arg1.getWidth(), 0, 0, arg1
.getHeight(), arg1.getLeft(), arg1.getBottom());
} catch (BadElementException e) {
e.printStackTrace();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (DocumentException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
In your main class, where you are creating PDF, pdfpCell.setCellEvent(new BGClass()); where pdfpCell is the cell for which you want background image.