Can I change the way pdf-reports are generated?

What I want to do is giving the first page of a pdf-report a certain layout, adding some stripes and geometric layout stuff, changing the font-size etc.

How can I do that, are there functions as I know them from fpdf for PHP?
However, I did not find any way to change the layout of the pdf documents :S Probably I have to dig into the code. Do you know where the pages are actually drawn into pdf-Format?

Thanks in advance!