Yes, backwards compatibility is a must. Nobody should have used any other module directly, nothing was documented that way (and the module source is almost devoid of any comment), so the chance is slim. Of course, there always might be that daredevil who knows better.

I did check the others on the same namespace (PDF::<xxx>) and there is a bunch, but nothing will collide. I thought to rename them anyway (PDF::Create::Page -> PDF::CreatePage, PDF::Image::GIF -> PDF::CreateGIF) to make it obvious that they belong together.

I'm worried too about side-effects of CPAN. For example, what will happen to the (now orphaned) subdirectories ?