Referrer URL Not working with lightbox

[Anonymous]

We have the form embedded into the HTML of our site, but have issues with the referrer URL due to the lightbox. Specifically, our website has a lightbox before accessing some PDF files, when the user fills out the form they are redirected to the PDF. However, we are not tracking accurately which resource.

I've written some javascript that can send through the final URL for where the PDF lives, but I don't know what hidden input field to send it to Marketo through. We tried the lpurl which did not seem to work.

Any suggestions? Forgive my noviceness. 

[SanfordWhiteman]

A lightbox will not affect the Referrer URL unless (and this a bad idea) it always loads the form into an IFRAME. Please post a link to the page in question.