GTMust is correct. Unless it is a high grade plywood, It will have knots in it. Also, the grain is going to be a lot different that a scale sheet of plywood will have. Here are a couple of pictures to give you an idea of what most plywood looks like
This is a high grade plywood
Lower grade
Here is a pic of the most common and cheapest plywood. It is called CDX. Do a google search for CDX plywood and you will find a few other helpful pictures. This is probably the look you want for the sides of a utility trailer.
BTW, I work in a lumber yard so I am around plywood all day
STewart