I\'d like to be able to write/overlay text over an existing pdf document using PHP. What I am hoping to do is have a pdf document that can act as a template, and fill in the
You probably want to use PDF Forms for what you want to do. To fill these babies you could use the FDF method described here: Using HTML forms to fill in PDF fields with PHP and FDF.
There is actually another nice SO post about PDF form filling here: Filling PDF Forms with PHP.