Thanks a lot!!
At PDF export use 'Spreads' to print to one large page.
I'm assuming that your pages are either single or two side-by-side.
Setting the pages to Spreads at PDF export won't merge all the pages together unless they are all in one two-page spread.
To do that turn OFF, Allow Document Pages to Shuffle in the Pages panel menu.
Then drag the pages next to each other until you have ten on a single spread.
Then you'll be able to export as a PDF spreads with one very wide spread.