Trying to get a video to launch other Symbols at certain time frames. How?

So here's my situation:
On my Stage, I have a video that's 3 minutes long. I also have a Container for a PDF. When the video gets to 30 seconds, I'd like have a PDF load into the Container. How do I set this up?
(Note that I know how to load the PDF, it's getting the PDF to load at the right time that I'm having an issue with. )
Thanks