I recently had a problem like this embedding a pdf file. I found after struggling with this pdf file for a client the best solution was to just code the pdf file in to a page of the site. it was a very large form application for a staffing company. It ended up looking more professional and aloud for the site to be more user friendly. Also it allows me to update the form easily when they need to add or remove fields.
The best part of it is the ability to let people fill it out in the browser and then email the form to the customer when the form is submitted with php. Obviously this may not be an option for you but just wanted to throw it out there. I hope that helps.