Ubuntu :: Open/Libre Office And Microsoft Word: Text Spacing And Display

I have Ubuntu 10.10 and Open Office 3.2.1. I guess that this problem may affect Libre Office too, but I will be happy to be proved wrong about that. I am editing a document that was originally produced in Microsoft Word (the standard .doc format). It is a form produced by a national organisation and it has to be sent back to them, and when submitted it has to be no longer than two A4 pages. It contains a series of headings and (expanding) text boxes for content.

In order to be sure about the length, I did most of the editing with Microsoft Word on my wife's laptop. On that machine, and on a PC that has a different version of Word, the document fits exactly within the two-page limit. But on my laptop, using Open Office, it appears considerably longer, taking up two-and-a-half pages. Why is this, and can anything be done to correct it? Open Office appears to be using the same fonts as Microsoft Word - the font names are the same, anyway - and the font sizes are the same, yet the text appears to take up more of the page display.