Overlay PDF

"Fit page" scales the overlay up or down until it fits inside each page without distortion and centres it, which may leave margins. "Stretch" covers the whole page, distorting it if the proportions differ. "Actual size" keeps its original size, centred, so a larger overlay is cut off at the edges. All three measure the part of the page a viewer shows, so a page trimmed with a crop box is fitted by its visible area, and only the visible part of the overlay page is used.

It was drawn with Layer set to "On top", the default, which paints the overlay over the page's content: if its page has a background, such as a white rectangle behind a letterhead, that background covers whatever lies under it. Under "Placement", set Layer to "Behind content" to draw the overlay underneath the page's own text, or to "Multiply" to keep it on top but let its white areas drop out. "Multiply" is the choice for a scanned base page, whose own opaque image would hide an overlay placed behind it. Lowering the Opacity slider also lets the text show through.

No. Some PDFs store a page one way up and carry a rotation setting that viewers apply on display, which is common in scans. The overlay is placed against the page as a viewer shows it, so it lands upright, and "Fit page" sizes it against the width and height you see. A rotation setting on the overlay's own page is honoured too: the overlay appears the way it does when you open that file on its own.

Yes, when the overlay PDF has more than one page. Choose "Cycle pages" and base page one gets overlay page one, page two gets page two, and so on, starting again from the first overlay page when the overlay runs out. "First page on all" ignores the rest and repeats page one.

Usually, yes. The visible appearance of each filled field is painted into the overlay as part of its drawing, so the answers appear on every stamped page but cannot be edited there; the overlay's fields themselves are not copied. Some form fillers save the values without redrawing the fields and leave the viewer to do it, and those answers come out blank or out of date. Run such a form through Flatten PDF first, which also works in your browser and redraws the answers into the page, then use the flattened copy as the overlay. An overlay page with no content stream and no visible field, stamp or comment is skipped as blank: the base pages it maps to are left unchanged and the result names it.

Each picker refuses an encrypted file the moment you add it, and that includes a PDF with no open password whose printing or copying is locked, because those permissions are enforced through encryption. Unlock PDF can remove the protection given the open password or, for a permissions-only file, the owner password. Unlike this tool, Unlock PDF uploads: the PDF travels over TLS to pdf.xyz's secure server, the input is deleted when the job finishes, the unlocked copy can be downloaded for 60 minutes, and a daily storage rule erases the stored copy after that.

Not fully. The page and its processing engine load over the network, and parts of the engine are fetched the first time a step needs them. The processing itself runs on your device.

Up to 100 MB per file.

Yes. Save it as a PDF and add it as the overlay: its first page is drawn over every page of your document. With a multi-page overlay you can choose “Cycle pages” instead, to use its pages in turn.

Fit page: Scale to fit, keeping the overlay's proportions (centered). Stretch: Stretch the overlay to exactly cover each page. Actual size: Place the overlay at its original size, centered. Your own pages keep their size either way.