Visio Pages can be set as Background or Foreground Pages. The Background pages appear in italics. When you choose to print the pages, it will show only the Foreground Pages.

If this is what has happened to your document, you can Right click on the page tab and choose Page Setup...
On the Page Properties tab of that dialog you can change the Page Type to Foreground.

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Andrew Lockton
Chrysalis Design, Melbourne Australia