Pick the file, then choose text, an image, or neither if you only want page numbers.
Size, opacity, angle and position. Tiling suits a NOT FOR DISTRIBUTION notice.
Choose position and format; you can skip the cover or start from any number.
A new file is produced; the original is left untouched.
The common approach renders each page to an image and stamps on top, which destroys the text layer and usually makes the file bigger. Here a drawing instruction is appended to the original page, so text, links and bookmarks all survive and the output stays searchable and copyable.
The standard fonts built into PDF cover Latin characters only, so writing CJK text directly fails on encoding. Text watermarks are therefore rendered to a transparent image on your own machine first — embedded once and reused on every page, so the file does not grow with the page count.
For a watermark that sits over body text, around 15% is the sweet spot: obvious on screen, still readable when printed. Tiling the page at an even lower opacity is what you need when the goal is to make screenshots less useful — at the cost of legibility.
Some PDFs already have numbers printed on the page, and adding another layer gives you a lone 5 sitting next to an old 5. Check the original footer first, or use Skip the first page to leave the cover out.
A watermark is a label, not protection. It states ownership and raises the cost of redistribution, but anyone can screenshot or photograph the page. Real restriction needs encryption and permissions, or simply not handing out the original.
No. Non-Latin text is rendered to an image locally and embedded, so it does not depend on the PDF's built-in fonts.
An image watermark is embedded once and reused, typically adding tens of KB; text is smaller still. A big jump usually means a very large image was used.
Currently it applies to the whole file. To stamp a few pages, split them out with Split PDF first and merge afterwards.
Yes. It is added drawing content, so a PDF editor can delete it — which is exactly why it is a label and not a security measure.
Three numeric formats are offered: 1, 1 / 10 and - 1 -. They render reliably in every reader and printer.
No — unlock it first. Order matters anyway: watermark before encrypting, never after.
No. It is drawn inside the page content area; the paper margin is decided by the printer's scaling setting, not by the watermark.