Why shouldn't a cover page be numbered "1"?

Convention, mostly — a cover or title page is identified by being unnumbered, and the reader's eye treats the first visible number as the start of the actual content. It's the same reason book title pages and half-title pages never carry a folio.

Why do some documents use Roman numerals before Arabic numbers?

It's a long-standing print convention: front matter — table of contents, preface, foreword — gets small Roman numerals (i, ii, iii…), and the numbering resets to Arabic (1, 2, 3…) at the first page of the actual body. A reader can tell at a glance, without reading a word, whether a given page is front matter or content.

Guide

Numbering PDF Pages — And Which Ones Not To Count

Adding a page number sounds like the simplest possible PDF edit — until the document has a cover page, or a photo inserted mid-way through that isn't really "page 14" so much as an appendix that happens to sit there. Numbering every page identically usually gets this wrong. Which pages get a number, and what number they show, is really two separate decisions.

Why a cover page usually goes unnumbered

A cover or title page is identified by the absence of a number — the reader's eye treats the first visible folio as where the document actually starts. Numbering the cover "1" doesn't break anything mechanically, but it reads as a mistake to anyone familiar with the convention, the same way starting a book's page count on its title page would.

Roman numerals for front matter, Arabic for the body

Longer documents often split the difference further: a table of contents or preface gets small Roman numerals (i, ii, iii…), and numbering resets to Arabic (1, 2, 3…) at the first page of actual content. It's a signal a reader can register without reading a word — front matter looks different from the body, on sight.

Skipping a page in the middle, not just the start

The harder case is a page that isn't at the beginning at all — a full-page photo or diagram inserted into an otherwise text-numbered report. Numbering it like any other page makes the count technically correct but visually odd; leaving it out entirely means whatever numbered the rest of the document needs to treat the sequence as having a gap, not just a starting offset. That's the difference between a tool that only supports "start numbering from page N" and one that supports arbitrary page ranges — HerePDF's page numbers tool does the latter: define more than one range, and the pages outside all of them are simply skipped, with numbering continuing correctly on the other side of the gap.

What "Page X of Y" should actually count

When a document shows "Page 3 of 12," most readers assume Y is however many pages they're paging through — not the PDF's raw physical page count. If three pages are deliberately excluded from numbering, the total should reflect that: the last numbered page should read "of 9," not "of 12." Getting this wrong is a subtle enough mismatch that a reader will notice something is off without immediately being able to say what.

After merging documents

Numbering is often the last step after combining several documents into one — a set of chapters, or several scanned sections — since the individual files' own page numbers (if any) stop meaning anything once they're combined. HerePDF's merge tool combines the files; numbering the result is naturally the next step.