Two things to check:
One possibility is that the table is wrapped. If Text wrapping is
enabled, Word won't allow the table to continue on following pages;
instead, its bottom will disappear off the page. Place the cursor
inside a cell and choose Table>Table Properties. Click the Table tab.
Is "Text wrapping" set to "Around"? If it is, click "None", and then
click OK.
Another possibility is that the text which you can't see in Print
Preview has been formatted with the hidden attribute. In Print Layout
view, select the text that doesn't display in the print preview, and
choose Format>Font. Click the Font tab. Is the "Hidden" option
checked? If it is, clear the option and click OK.
