There are no tools I'm aware of that automate pulling a PDF in as a FileMaker layout. You can either put it on the background as an image (don't recommend), or you can build it using FileMaker tools. You're doing to need to put FileMaker fields on it anyway, if you want the data in the system.
Not the answer you wanted, I know. But I think, in the long run, you'll be much better off with native FileMaker tools for performance purposes.