Electronic Forms Project - Advice / Research Needed

I am seeking advice on a programming issue my client is facing; this project involves no actual work other than perhaps some research. My client is only going to pay for advice that leads to a solution to his problem. Situation: We have been dealing with PDF files and how to populate them with data. My client's website's users will be uploading PDF files; this means we do not always know the content on them beforehand or even if the PDF is interactive. Possible Solutions: #1 - Users pay a small fee to create an interactive version of their form. Form fields would correspond to variable names; I can use these variable names to populate the form. #2 - We create functionality like DocuSign where the user clicks on a canvas (with the PDF loaded on to the canvas) and then starts typing. #3 - Have the user enter information into forms. Use a programming language such as ColdFusion, PHP, ASP, JSP, etc to create the needed form. #4 - A combination of the above. Try to think of a solution that we have not thought of. There are issues with the above solutions in that my client wants a solution that will work in all circumstances.