Every year, hundreds of millions of documents are notarized in the United States: wills, mortgages, citizenship forms, handgun applications. While for decades, this has all been done in person, there is a budding crop of sites that allow notaries to take their services online. If you’re already a notary, you can sell your services online. Or, if you want to get started, check out the National Notary’s checklist for becoming a certified notary.
If you have pop-ups and optins on every page, I would have to think that it would be a lot harder to convince someone to link to it. Especially since the pages where you have your optins (and probably receive the most traffic) are probably the same pages that you have your best content on as well that you'd be hoping to pitch in your outreach campaign.