LaTeX: How to set the pdf dpi when using images -

i'm writing thesis in latex , have troubles image imports.

i want thesis pdf, imports jpeg images of charts , other things. i'd have higher resolution; default miktex settings have image resized crappy resolution.

i'm using miktex, adobe reader 9.4, win7 32.

how can raise resolution of pdf produced latex sources?

is there other way insert pick without losing resolution?

i know vectorial formats, have bmp or jpg insert in thesis.

a part of code this: (the first 2 rows doesn't work =/)

\pdfpxdimen=2in     \divide\pdfpxdimen 300  \documentclass[12pt, a4paper]{report}  \usepackage[italian]{babel}     \usepackage[t1]{fontenc}     \usepackage{graphicx}  \begin{document}  \include{frontespizio}  \newpage  \include{ringraziamenti}  \tableofcontents   \newpage  \include{introduzione}  \pagenumbering{roman}   \pagenumbering{arabic}  \pagestyle{fancy}  \lhead{} \chead{} \rhead{\scriptsize \leftmark} \lfoot{}  \cfoot{\thepage} \rfoot{}  \renewcommand{\headrulewidth}{0.1pt}  \include{capitolo1}  \newpage  \end{document} 

and image calling is:

\begin{figure*}[h]         \centering             \includegraphics[width=\textwidth]{usecase.png}         \label{fig: use cases}     \end{figure*} 

first of all, suggest use .png images.

if still want change dpi may insert code on .tex preamble:

\pdfpxdimen=1in

\divide\pdfpxdimen 96

(for 96dpi)