Well, for example i can open a pdf file like this:
$pdf=PDF::API2->open("HelloWorld.pdf");
but i don't know how to traverse through the objects, or read the text in the file or anything, i can pretty much just write on top of it.

Also when creating a pdf file i find that i can't judge the page limit to format the page correctly, e.g. if a line is too long it just goes off the page.
my $page = $pdf->page;
$page->mediabox(200,200);
my $txt=$page->text;
$txt->translate(0,0);
my $font=$pdf->corefont('Courier-Bold',1);
$txt->font($font,50);
$txt->lead(50);
$txt->text('If i make this line too long it will disappear off the end of the page');