Some changes reach many books at once: the publisher's name or emblem, an author's name, the copyright page's settings, an ebook look or a print type style. Each file the studio built before such a change says it's out of date on its book's page. Rebuild books, on the Books page, gathers them all.
Choose what to build again. The files are listed by why they're out of date, with their books and editions: "Built before the publisher changed", "Built from an older manuscript", "Not built yet" (for a format whose edition has a manuscript), or "Its last build didn't finish". Tick a whole group, or single files, and press Rebuild.
They're built one after another. A run hands in two files, then one more as each ends, so everyone's builds keep moving. Each file builds as it does from its own book's page, with the same checks and report, and the page shows how far the run has got. Stop hands in no more; files already on their way still build. One run at a time for a team; up to 500 files in a run.
Bulk rebuilds come with the Publisher plan. Building files costs nothing, one at a time or all together.