I used Aftereffects to combine a video with a Photoshop file. I rendered it out as an mp4 so that I can upload it to a website. Now I want to be able to watch the video and talk over the top of it and record it while the video is playing. And then render it again so the sound is with the video as an mp4. Can I do this in Audition or should I be doing it in Premiere or Aftereffects?
Yes, you can import the video into the Audition multitrack timeline, then record and assemble new audio. Use File > Export > Export to Adobe Media Encoder... to merge the multitrack audio with the original video footage in AME.