A common source of confusion: unlike a Word document, where page numbers are a live field that recalculates automatically as content shifts, page numbers added to a PDF are baked into each page as static text once the numbering tool runs. They "survive" edits in the sense of not disappearing or looking corrupted, but they don't automatically stay accurate if pages are later added, removed, or reordered, since a PDF page's number isn't a dynamic field, it's just text placed at a specific position on that specific page.
Why manually typed numbers are the real problem
The failure mode this question is usually really about is someone manually typing "1", "2", "3" onto each page individually, then inserting a new page in the middle later, at which point every subsequent number is now off by one and has to be fixed by hand. Using Add Page Numbers instead of manual typing avoids this specific failure during the initial numbering pass, since it numbers the entire document sequentially and consistently in one operation rather than page by page.
The right order of operations
The most reliable approach is finishing all structural edits first, adding or removing pages, reordering with Organize PDF, inserting blank pages with the PDF Blank Page Inserter, and only running Add Page Numbers as the last step before finalizing the document. Numbering last means the sequence reflects the document's actual final page order and count, rather than needing to be redone after every subsequent edit.
If a document does need another edit after numbering was already applied, the practical fix is re-running the numbering tool over the whole document again rather than trying to manually patch individual page numbers, it's faster and avoids the off-by-one errors that come from editing numbers by hand.
Numbering that needs to persist across separate documents
For legal or compliance documents where numbering needs to stay continuous and traceable across a large set of files, even ones assembled from multiple source documents over time, PDF Bates Numbering applies a persistent, sequential identifier (not just a page count) across an entire document set, which is a different and more robust need than simple page numbering for a single file.