Place numeric labels in the visible page area
Merge accepts up to 20 PDFs; every other tool accepts one PDF. Each PDF is limited to 50 MiB, inputs are limited to 200 pages, generated downloads are limited to 100 MiB, and each run has a 60-second cancel/timeout boundary. Password-protected PDFs are rejected; these tools do not remove passwords. Labels use numeric text and an embedded font, positioned from each page's crop box and rotation.