Because After Effects can easily convert film (24 fps) to video (29.97 fps) using 3:2 pulldown, you can perform a clean PAL-to-NTSC transfer by setting up 25-fps PAL video to act like 24-fps film. This lets you apply 3:2 pulldown to the footage when converting to 29.97 fps. This technique works particularly well for progressive (noninterlaced) PAL video.
To preserve audio synchronization but slightly lower the pitch, choose Layer > Time > Time Stretch, and then enter 95.904 in the Stretch Factor box.
To preserve audio pitch but not synchronization, or for clips without audio, right-click (Windows) or Control-click (Mac OS) the footage item in the Project panel, select Interpret Footage > Main, select Conform To Frame Rate, and then enter 23.976 in the Conform To Frame Rate box.