There are quite a few ways to move things back and forth between Premiere Pro and After Effects. You can copy and paste; you can import projects; you can import rendered intermediate files; if you have the Production Premium or Master Collection suite, then you can use Dynamic Link…
Here’s a page that summarizes the interaction between After Effects and Premiere Pro:
“Working with Premiere Pro and After Effects”
If you are going to use a rendered movie file as an intermediate, then be sure to use a lossless codec. A tried and true intermediate format is a QuickTime movie with the video encoded with the Animation codec at the highest quality setting.
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Todd Kopriva, Adobe Systems Incorporated
putting the ‘T’ back in ‘RTFM’ : After Effects Help on the Web
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