How do I calculate the autocorrelation of a train pulse having only the pdf?
Suppose that your pulse train is denoted $X(t) = Y\cdot g(t)$ where
where $g(t)$ is the basic pulse train and $Y$ is the random
amplitude of the pulse train.  Then, $X(t)$ is not a 
wide-sense-stationary process and its autocorrelation function is
$$R_X(t_1,t_2) = E[X(t_1)X(t_2)] = E[Y^2]\cdot g(t_1)g(t_2).$$
If $Y$ has mean $\mu$ and variance $\sigma_2$, then 
$E[Y^2] = \mu^2+\sigma^2$.  If $g(t)$ is a function of period $T$,
that is, $g(t) = g(t+T)$ for all $t$, then $R_X(t_1,t_2)$ is
periodic in both arguments:
\begin{align}
R_X(t_1+T,t_2) &amp;= (\mu^2+\sigma^2)g(t_1+T)g(t_2) 
= (\mu^2+\sigma^2)g(t_1)g(t_2) = R_X(t_1,t_2)\\
R_X(t_1,t_2+T) &amp;= (\mu^2+\sigma^2)g(t_1)g(t_2+T) 
= (\mu^2+\sigma^2)g(t_1)g(t_2) = R_X(t_1,t_2)
\end{align}
I am quite sure that this is not what you hoped to hear and so you
must revise your question appropriately, giving more details and
describing more clearly what it is you want to find out.