Not sure what your goal is here, but there is an opensource php-library called fpdf, which also has an extension for taking a pre-made pdf as layout and then populate it with more content, generating a new PDF with that info.
However, I would go for a solution that you can integrate nicely into the plattform you're building, but I wouldn't go in a HTML->PDF solution since you won't have any clue about what would fit on a piece of paper regarding sizes in that kind of enviroment, meaning you won't know when you should split the content into two separate templates.