将图像附加到正确位置的现有PDF

So, here's the thing, we have a bunch of pdf forms for users on our website to fill out, we have a submission button inside every pdf form that sends the filled data through a http post method. We are already doing a pre-filled form, where the user fill general information on a html form, data that are used to generate a partially filled multiple pdf files, so whatever the pdf form the user has selected to fill, all of them will be regenerated having the pre-filled information that he just typed on the html form. I accomplish this by using pdftk (So, here's the thing, we have a bunch of pdf fo