If a PDF is more than a few pages long, page numbers are not decoration. They make review possible. "Look at the chart on page 18" is much easier than "scroll down near the end."
For formal documents, use a quiet footer such as Page 3 of 12. For internal drafts, a small top-right badge can be easier to spot. If the PDF has a cover page, start numbering on page 2 while showing the first visible number as 1.
Pagivo's Page Numbers tool now includes templates, placement, formats, start number, first numbered page, font size, and color.