The format string attack on printf you mentioned isn't specific to the "%x" formatting - in any case where printf has more formatting parameters than passed variables, it will read values from the stack that do not belong to it. You will get the same issue with %d for example. %x is useful when you want to see those values as hex.
As explained in previous answers, %08x will produce a 8 digits hex number, padded by preceding zeros.
Using the formatting in your code example in printf, with no additional parameters:
printf ("%08x %08x %08x %08x");
Will fetch 4 parameters from the stack and display them as 8-digits padded hex numbers.