How do you change PAGE size (not paper)?

All I want to do is set up an 11x17" document page but can’t find the option anywhere! I find lots of suggestions here for changing the paper printing size, but I need a one page document page that is 11x17 portrait. HELP!

On Writer page formatting (all of it) is managed through page styles. On the status toolbar (lower part of Writer’s window), between the word count and the language name for the text you can see the name of the page style currently in use: click on that name and, on the Page tab, change the values according to your needs.

You can later create a template from that document and set that template as the default one.