Number a document properly
Merged bundles arrive unnumbered, and anyone who has had to discuss "the page after the one with the table" knows why that is a problem. Court filings, tender submissions and assembled application packs generally require numbering.
Choose a position, a format and where to start. The numbers are drawn into the pages, so they are there for everyone who opens the file.
It adds almost nothing to the file
This uses Helvetica — one of the fourteen standard PDF fonts every reader has built in — rather than embedding a font file. That is the difference between a few hundred bytes and a few hundred kilobytes.
It matters more than it sounds. People numbering a document are usually about to upload it somewhere with a size limit, and a tool that quietly adds half a megabyte for a nicer typeface is not doing them a favour.
Rotated pages are handled
If a page carries a rotation — common in scanned bundles where one sheet went through the feeder sideways — the number is positioned relative to how the page is actually displayed, not to its underlying coordinates. Without that, numbers end up running down the side of the page.
Starting number
Set it to 2 when there is a cover page that should not be page 1. Set it to 47 when the document continues from a previous volume. The count runs on from wherever you start.
If a cover page should carry no number at all, split it off first, number the rest, then merge them back together.