Sorry, but if Apple's policies are applied consistently (I know they often aren't), this won't fly.
I have an app with a basic email/password sign-in screen (the app represents a small part of a larger web-based SaaS product). Apple has rejected my app for including anything in the app that even remotely hints to the service existing outside of the App Store. This includes a "Sign Up" button linked to the web signup, a "Learn More" button that links to the website, or even a "Support" button that has navigation that can lead to a signup or pricing page. After a long chat with someone from the App Store review team, I learned that you can't link to any page of a site that contains other links that can indirectly lead to a signup or pricing information. It's a pretty harsh policy.
So my app was finally approved, but without any links to support documentation on my site. Congratulations, Apple - you win :)