How PDF page numbering works, and how to get it right
What a stamped page number really is, why it can differ from the page label in your viewer, and how to number front matter cleanly.
A stamped number is just drawn text
Adding a page number does not change the PDF's internal page order or its structure. The tool simply draws a short text string onto each page at a fixed anchor, the same way a rubber stamp lays ink on paper. That string becomes part of the page content, so it prints and shows everywhere the page does. Because it is drawn rather than computed by the viewer, it stays put even if someone later reorders or extracts pages.
Page number versus page label
A PDF viewer often shows two numbers: the physical sheet index and an optional page label baked into the file, such as roman numerals for a preface. The number this tool stamps is independent of both; it counts up from the start value you choose, one per physical page. That is why setting the start to 10 makes the first page read 10 and the fifth read 14. If you need the visible stamp to match a viewer label, choose a start value that lines them up.
Handling front matter and offsets
Reports frequently have a cover and a table of contents that should not count as page one. Since the tool numbers every page from your start value, the cleanest approaches are to split off the front matter, number the body, then rejoin, or to accept an offset by starting at a value that makes the body read correctly. There is no skip-first-page toggle here, so plan the start number around the pages you actually want counted. Keeping the font size modest, around 10 to 12 points, keeps the stamp unobtrusive in the margin.
Why in-browser stamping keeps files private
Many online PDF tools upload your document to a server to process it, which is a poor fit for contracts, medical records, or anything confidential. This tool loads the file into your browser's memory and runs pdf-lib locally, so the bytes never travel over the network. The result is generated on your machine and handed straight to a download. Nothing is stored, logged, or transmitted, which is the safest posture for sensitive paperwork.