Question: I'm building what will be a PDF in Sketch 3. 

I want to create a button (a rectangle box with "sign up" inside) that launches a mailto link when the person reading it clicks on it. 

I can't figure out how to 1) add links in Sketch, or 2) make the entire button (including the border of the rectangle box) clickable, vs just the text portion. 

Any help is appreciated!

Answer: 
Found this on the Sketch Talk forum. Just confirmed that it works, even with mailto: links.

"Easiest way (which is how I did it in Illustrator too) is to paste the URL you want over the text you want to hyperlink, change the URL color to the same as the background, and send it to the back underneath the original text you wanted to link. Once you export, there will be an invisible hyperlink underneath the text!"
A simple solution is for this problem is here

<https://youtu.be/WLggIppVE1w>