Merged documents almost always need numbering afterwards, and court filings, contracts and printed handouts need it as a matter of course.
Choose where the number sits, what format it takes — plain, 'Page 3', or '3 of 40' — which page it starts counting from, and which pages get one at all. Cover sheets and title pages usually shouldn't be numbered, and front matter is often numbered separately, so both are straightforward here.
The numbers are drawn into the page content rather than added as annotations, which means they print exactly as they appear and can't be selected and deleted by whoever opens the file next. On documents that mix page sizes — a Letter report with an A3 foldout in the middle, say — each number is positioned relative to its own page, so they stay in a consistent place visually.
Combine files into one PDF and set the order before you merge.
Break a document into separate files by range or interval.
Drag pages into a new order, rotate or drop the ones you don't need.
Turn sideways or upside-down pages the right way up.
Pick pages to drop, visually or by range.
Keep only the pages you want as a separate file.
Combine JPG or PNG images into one PDF, with page size control.
Render pages to images at the resolution you choose.
Shrink a PDF with a side-by-side quality preview and a size target.
Add a searchable text layer to a scanned document.
Extract text as plain text or Markdown, in reading order.