It sounds like a Page Setup setting. In the same way that you can left/right/centre or justify a paragraph alignment, you can do the same with vertical space in a section.

Have a look at the Page Setup > Layout > Vertical Alignment. By default, this is usually set to Top but your description sounds like it might be set to 'Justified' instead.

Note that page setups apply at the section level so if your document contains more than one section you might need to apply the changes to the Whole document or work through section by section.

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Andrew Lockton
Chrysalis Design, Melbourne Australia