How can I pitch an audio signal?
Does a "pitch shifter" object exist in pd?

Help->Browser->3.audio.examples->G09.pitchshift.pd

yes I've read it but I don't realy understand how it works....
Can anyone give some help?

You mean how it works or how to use it?

To use it, just replace the [pd test-input] with your own audio signal. Then adjust the number box labeled "transposition" to change pitch. If you need to, adjust the "window" box.

It is a granular pitch shifter that works by sending the signal into a short delay, and then reading it back with two delay taps (the two grains). The [phasor~]s adjust the delay times, thus reading them back at different speeds, depending on the transposition, which is what causes the pitch change. They also control the grain envelope (window) and are 180 degrees out of phase with each other, causing them to fade in and out of each other. Since each grain always starts off reading at the same delay time, they're essentially able to read them at different speeds without "falling behind" or "getting ahead" because they end up wrapping back when their envelopes are silent. It's kind of a difficult thing to describe while trying to keep it simple, but hopefully that helps.

Ok I understand.
But isn't there an easiest way to make a simple pitch shift?

Just copy and paste, you don't have to really make anything. All the work has already been done for you here. If you want you can turn it into an abstraction, then it's as easy as using an external object.

unfortunately there is no such thing as a "simple pitch shift". it requires a fair bit of circuitry or code, and thus in pd, you get a patch with that code too.

Very good guide to pitch shifting is available here: http://crca.ucsd.edu/~msp/techniques/latest/book-html/node115.html
However, it may be difficult to understand, it you are new to digital sound processing.