Repeating your primary call to action (CTA) can be very powerful, especially on long or large pages.

Now we're not saying stick it on the page between each paragraph.  Once at the top to show people what the CTA is, and then again further down at the bottom of the content to remind people of the action to take should be enough.

When reading a page most users will pause for a second to decide what to do next, leave the site or go to another page for example.  If we can grab their attention with another, well placed and worded CTA then we're more likely to get the user to do it.