With modern Analytics packages measuring your conversion/retention funnel is easier than ever, and I encourage you to do so.
For maximum return, don’t forget that what happens between between touch points (the gaps) in the funnel is critical.
White papers downloaded and successful signups are both great metrics to measure, and those pages are great to A/B test on, but what you need to remember is that between these steps (pages) there is something going on that you can’t see, an invisible step you can nether the less optimise/influence and its a great opportunity to convert more customers.
By engaging them in the time gap between conversion via email or social.
Convert more people who have downloaded your white paper by asking them what they thought of it via twitter, or by offering a discount via email.
As an aside: retargeting ppc at this point may be a good idea
Another example: did a person setup a free account but has not returned to using it? Send a retention email to remind them why they signed up. Nine times out of ten if a user tries your product/service twice, they will become a regular user.
Thats it! its nothing revolutionary, but it works and is another weapon in your arsenal of many tricks to increment your conversion rates upwards.