Just download the zip file from the site. Unzip to some folder in your document root.
Create a new file and add the following code to see the effect in a second. You will also find some example in the readme.pdf, packed in the zip file. You can also have html tags in the passed string. Isn't that 5 lines of code amazing?
$doc = "Hello World!!!!";
$pdf =& new Cezpdf();