TL;DR: Upload a background PDF and a foreground PDF — download a copy with foreground stamped over every background page.
Overlay PDF pages online — layer one PDF document on top of another. Perfect for adding letterhead, branded backgrounds, or watermark stamps to existing PDFs.
Overlay PDF is part of PrivaTools — a free, open-source alternative to iLovePDF, Smallpdf, and Adobe. Server-side tools process your file in an isolated container and discard it immediately; many tools never upload at all and run entirely in your browser.
Merge concatenates files page-by-page. Overlay composites pages on top of each other — useful for adding letterheads, watermarks-from-PDF, or repeating templates.
By default it applies cycle-wise: if the overlay has 3 pages and the base has 10, the overlay repeats. For one-time overlay, use a base + overlay of equal length.
Yes — PDF supports transparency and the overlay's alpha is honored. White rectangles still cover what's beneath; transparent regions show base content through.
See how PrivaTools compares to iLovePDF, Smallpdf, Adobe Acrobat, and other free PDF tools.