The most straightforward way is to ask, ask customers reading content, to take a next step. To subscribe to your newsletter. To download a whitepaper. To explore the products. You need to ask and give them that step to turn them into leads!
That seems so silly, but are you asking them? Or are you asking them enough? Make sure that calls to action are in the flow of the content. As users would use your webpage. Buttons off to the side they may not see. So consider placing them within the content. Be tasteful about it. But put yourself in your customer shoes, they click on this link, they scroll down here, they stop reading and they go where.
Make sure you measure your lead conversions too. So you can identify your top pieces of content, devices, where leads come from, times of day, traffic sources, how much attention they pay to content. That way you find ways to get more leads from your content investments.