Signing an embedded PDF in Storyline

You could have them answer an quiz question that asks them to acknowledge they have read the PDF.

• For example, that could be a single-response question with just one response, or a T/F question where they answer "Yes" or "No."
• Obviously, if they answer "No," you'd need to program it so they couldn't continue. Or, at least, so they'd know they'll be in trouble.  :-) 

To have the answer reported for compliance, you'll need to include a Results slide. But you could redesign it so it doesn't look like one.