From the Help file->Designating printable frames
Designating printable frames
All frames in the specified Timeline print by default. You may want to limit the number of frames that can print—for example, if you have a lengthy animation of dozens of frames. You can designate specific frames in a movie as printable in order to print only those frames; unspecified frames won't print.
To specify frames as printable, you label the frames.
To designate printable frames:
1 Open or make active the movie that you want to publish.
2 If the Frame panel isn't visible onscreen, choose Modify > Frame.
3 Select the desired frame in the Timeline that you want to make printable.
4 In the Frame panel, for Label enter #p to specify the frame as printable.
5 Repeat steps 3 and 4 for each frame you want to designate as printable.
;-)