Frequently asked questions

What is a PDF overlay?

An overlay stamps the content of one PDF onto the pages of another — like printing two sheets on top of each other. Typical uses: applying a letterhead, a watermark page, a “DRAFT” stamp, or a form background.

What's the difference between overlay and underlay?

Overlay draws the stamp in front of the base content; underlay draws it behind, so the base text stays fully readable on top — the right choice for letterheads and backgrounds.

Which pages of the overlay PDF are used?

If the overlay PDF has the same number of pages as the base, pages are paired one-to-one. Otherwise the overlay's first page is reused on every selected base page.

Do my files get uploaded?

No. The overlay is applied entirely in your browser with client-side code — neither PDF ever leaves your device.