The direct-sale versions of our software have been designed to look for Apple’s proof of purchase certificates on your computer. So long as you have run the Mac App Store version at least once, you will be able to run the regular version as fully activated software, rather than in demo mode. – Installing the Direct-Sale Version as a Mac App Store Customer / Purchasing and Installation / Knowledge Base - Literature and Latte Support
So if you have run the Mac App Store version on your Mac, you should be able to download and run the Direct-Sale version without restriction. From there, you should be able to export your projects to Markdown.
And if that doesn’t work, perhaps the direct-download version will work in trial mode anyway, allowing you to export whatever you want.