If you insert the pictures 'in-line' with text, they will automatically move with the text. If you insert the pictures as anything other than in-line, their movement is governed by a combination of what they're anchored to and what page positioning has been assigned to them. When not inserted 'in-line' with text, they can also have a 'move with text' option checked.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]