I usually recommend against bundling print and digital subscriptions for most paid content sites, since it can really devalue your online/digital offerings, making them seem like a “bonus” feature instead of an independent service worthy of full-price subscriptions.But in this week’s Case Study on our sister site, Subscription Site Insider, The Successful Investor Network presents a good case for bundling.The Successful Investor Network decided to start publishing its monthly investment newsletters in PDF formats. Since the PDF formats contain the same information as the print newsletters (and, in fact, are embargoed until the print newsletters are in the mail), it makes sense that The Successful Investor Network would allow its print subscribers to access the PDF formats without paying more.By bundling, the site has been able to acquire more than 12,000 subscribers for its four newsletters and membership plan, and only 25% are print-only subscribers. This puts the 17-year-old company in a good position to get more of its subscriber base to engage online, especially through weekly email “hotlines.”Perhaps in the future the site can offer exclusive digital content and charge a separate price. In which case, they may want to consider breaking up their digital and online offerings like The Columbia Journalism Review is now doing.