Begin with an email blast you haven't sent yet. Before you send it you'll create a .pdf.
Go to Communication > Broadcasters > Email  > email_slug > Content. 

It might be a good idea to remove any smart fields you have used in this email before saving as a .pdf

When you are in the "Content" view of your email navigate to your URL address panel, delete the word content and replace with html_preview. To do so, remove the word 'content' from the url and replace it with html_preview in your tool bar. 

This gives you a really nice view of your email that you can print to a .pdf and save on your computer. 

Select Print to save it as PDF. To save it without any extra info uncheck 'Headers and footers'.

Now, create a page on your website to hold your .pdfs. In this example, I made a blog post that I can always go back to. 

In page Files, upload your .pdf and right click to copy the link address. 

Within the page Content, I highlighted the text to link and clicked the link button to add the .pdf.

That's it! To see it in action, you can view Taylor's page & download her NB newsletter!