How to use Page Numbers in OpenOffice.org:

Usually, there are different sections which have different page numberings.  I usually have documents which have a title page with no page number, then the table of contents, etc. which have lowercase Roman numerals and start at ii, then the main section which has a regular numbering starting at 1.

To do this, you need a separate Page Style for each of the different numberings (3 in the above case).  On the Page Style dialog, go to the Page tab, then the Format combo box to decide what the page numbers will look like.  Note that applying a page style will not cause the page numbers to appear automatically.

Then apply the page styles.  Apply the one for the first page normally; however, for any other styles that need to be applied, you can't apply them the same way without setting all previous pages to that style too.  You have to do one of 2 things to get multiple styles:
1) If the page style is only for 1 page (such as the title page), go to it's page style dialog and set the "Next Style" to the one you want next.
2) If there are many pages with one style followed by another style (such as the Table of Contents and other introductory pages), you have to insert a Page Break at the end of those pages and give it another style which is the style for the following pages.  (Insert -> Manual Break).

To actually insert the page numbers, you normally insert a "Field" (a special OpenOffice.org object) into the header or footer.  The header and footer are areas such that if you put something there, it appears on all pages or on all pages with that page style.  So if you put a Page Number field there (Insert -> Fields -> Page Numbers), it calculates the page number for each of those pages and inserts it.

If you want the numbering to restart at 1 (or some other number) for a certain page style, you have to supply that information with the Page Break that you insert to change the Page Style.  There's an input called "Change Page Number".

This system is actually a really good way to handle page numbers - probably the best used by any word processor.  But it's hard to discover everything you have to do.