Microsoft Word Problem with Unexpected Page Breaks

I have been having an irritating formatting problem in Microsoft Word 365, but I think you can get the same problem in all versions of Word. The problem was after a sub-heading the following text would start on a new page. After much fiddling with Style settings and trying various fixes unsuccessfully, I eventually came across the fix that I have reproduced in full below on the Microsoft support website. 

It is counter intuitive, typical Microsoft, as you will see it involves removing the "Keep with next" option from the Normal Style, Paragraph format Menu.

Source: https://support.microsoft.com/en-gb/kb/233493

Check for unexpected page breaks following "Normal" style text

If a series of Heading styles is used in a document (an outline, for example) followed by text that is formatted with the Normal style, an unexpected page break may occur following the Normal text. This problem occurs only in normal view and does not occur in outline view. Use one of the following methods to remove individual occurrences of an unwanted page break.

Method 1: Apply the "Keep with Next" option to Normal text

Word 2000, Word 2002, and Word 2003

1. Select the Normal text.
2. On the Format menu, click Paragraph.
3. Click the Line and Page Breaks tab, and then click to select Keep with next.
4. Click OK.

Word 2007, Word 2010, and Word 2013

1. Select the Normal text.
2. On the Page Layout tab, click the Paragraph dialog box launcher in the Paragraph group.
3. Click the Line and Page Breaks tab, and then click to select Keep with next.
4. Click OK.

Method 2: Clear the "Keep with next" option from the heading

Word 2000, Word 2002, and Word 2003

1. Select the Heading text that precedes the Normal text.
2. On the Format menu, click Paragraph.
3. Click the Line and Page Breaks tab, and then click to clear the Keep with next check box.
4. Click OK.

Word 2007, Word 2010, and Word 2013

1. Select the Heading text that precedes the Normal text.
2. On the Page Layout tab, click the Paragraph dialog box launcher in the Paragraph group.
3. Click the Line and Page Breaks tab, and then click to clear the Keep with next check box.
4. Click OK.

Method 3: Permanently change the occurrence of unwanted page breaks

Word 2000, Word 2002, and Word 2003

1. On the Format menu, click Style.
2. In the List list box, click All styles.
3. In the Styles list, click Heading 1.
4. Click Modify.
5. Click Format, and then click Paragraph.
6. Click the Line and Page Breaks tab.
7. Click to clear the Keep with next check box, and then click OK.
8. To make the change permanent for the current document and all new documents based on the active template, click to select Add to template. Otherwise, the changes that you make will only affect the current document.
9. Click OK, and then click Close.

Word 2007, Word 2010, and Word 2013

1. On the Home tab, go to the Styles group, and then click the Styles dialog box launcher to open the list of styles.
2. In the Styles list, click Heading 1.
3. Click Modify.
4. Click Format, and then click Paragraph.
5. Click the Line and Page Breaks tab.
6. Click to clear the Keep with next check box, and then click OK.
7. To make the change permanent for the current document and all new documents based on the active template, click to select New document based on this template. Otherwise, the changes that you make will only affect the current document.
8. Click OK, and then click Close.

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