Create a capture form prior to downloading PDFs

Hi, I would like to ask advice about capturing form data before downloading PDF datasheets on one of our clients sites.

When we have done this previously, prior to using Perch (i.e. for brochure downloads) we would have used a simple form and then upon submitting, direct the user to a static confirmation page with a link to download the file. This serves OK if the PDF is a fixed file as it can be hard-coded into the confirmation page, however, I would like this to work with multiple files uploaded through Perch CMS and also on various pages...

Is there a way I can have the link go to a form (preferably in a pop-up window) then upon submission, go to the confirmation page with the download link in place...? E.g. 'Click here to download...' The problem I envision is working out a way to carry the data / link info through the form and on to the confirmation page.

I would appreciate any suggestions and open to looking into similar workarounds.