pdf figures in Kile not showing up in the .pdf [closed]

Question

I've started trying to include .pdf images directly into my .tex files (instead of converting them to .eps which seems to degrade the image quality) but they're not showing up in the final .pdf file. Here is the code I am using in Kile (Ubuntu dist. OS):

\include{graphicx}
...
\begin{figure*}
    \begin{center}
    \includegraphics{width=0.8\textwidth,natwidth=400,natheight=400]{fig.pdf}
    \end{center}
\end{figure*}

The figure doesn't show up in the pdf (just blank spaces) whether I compile from the command line, or use the Quickbuild in Kile.

I also would like to know how I can get around specifying the natural width/height - which will be a pain to tweak - as it seems I have to do otherwise the compiler complains about not finding a bounding box (the pdfs have been published from Windows Excel).

Any help will be much appreciated!