My main composition has the following specs:
Pixel Aspect Ratio: Square Pixels
Frame Rate: 29.97
The footage I'm trying to import has these specs:
Pixel Aspect Ratio: D1/DV PAL (1.09)
Frame Rate: 25
Right now, when I place the footage in the comp, the edges are fairly jagged. I assume there's some weird pixel aspect ratio thing that's going on, but just not sure how to get it right.
You have more than the aspect ratio problem going on. There is a frame rate mismatch. There is a very big problem of scale as well.
You can't expect to have as sharp an image as the original if you scale the layer to fit inside the comp side-to-side. There is a third-party plugin called Instant HD from Red Giant software that can HELP -- it won't CURE the problem of too few pixels.
You also need to change the frame rate of the footage to 29.97. AE's Time Warp can help with that. If your need to have an extremely good-looking frame rate conversion is critical, you'd again have to get third-party frame rate conversion software like Magic Bullet or Twixtor.