Survey Pop Up

Hello,

I would like to know what type of scripting could accomplish the following task:

We have one survey that we would like site visitors to answer in order to collect data for medical research purposes. The survey needs to pop up when users click a "download" pdf button on various pages in the site. Each PDF is different, but the survey is always the same. So, we need two things:

1. being able to tell which pdf the respondent wants so that they can be re-directed to the proper download url once they've completed the survey. Preferrably, this would be done without having to answer a question like "What PDF do you want to download".

2. if the respondent has already taken the survey previously, then the download button would skip the survey, and go straight to the pdf. Our current survey provider (Qualtrics) can tell when someone has already answered a survey when they are on a certain browser, but if this person answers from a different browser, then it can't tell that someone's taken the survey. So, my guess is that a script would be needed that would put a cookie on the users desktop?

The way we've thought of solving this is by simply asking the respondent to check a "which pdf do you want to download?" at the beginning of the survey, then re-directing that person to the proper url at the end of the survey based on their response, and just using the survey provider's way of finding out if someone has already taken the survey, even if it's not all that accurate.

But, if there is a more accurate and efficient way to do this, I would like to know what type of scripting language(s) it would envolve and how complicated it can get (i.e. is there a database that needs to be built.

Thanks for your time!

Different browsers are effectively different systems entirely for cookies and other identification. The only consistency is the IP address but that would change from time to time so it's not entirly reliable. You can use it for a limited time though (up to a day certainly) except that other users on the same network such as an Internet cafe or school would be seen as the same user.
It's not really practical to try to force them to be seen as one browser.

A serverside programming language like php would be good for the survey considering you need to store the results, probably in a database. I suggest either learning php and mysql or hiring someone because this is a custom project and fairly complex so you won't find an existing script that does it as is.