PDF Watermark

Diagonal center is the convention for status labels — CONFIDENTIAL, DRAFT, SAMPLE — readable at a glance without burying the content. Tiled repeats the text across the page and is the deterrent choice for documents you expect people to screenshot or re-share, since cropping can't remove it. Footer is for attribution that shouldn't shout: a name, date, or 'Prepared for X'.

15–20% for diagonal and tiled marks — clearly visible without fighting the text under it. Go lighter (8–12%) on dense text documents, heavier (25%+) on image-heavy pages where a faint mark disappears. The footer placement enforces a readable minimum since a ghost footer serves no one.

By a determined person with PDF editing tools, yes — the watermark is a drawing operation in the page content, and content can be edited. That's true of watermarks from Acrobat too. It reliably deters casual re-sharing and survives print/scan cycles, which is what watermarks are actually for; genuinely sensitive content needs redaction or access control, not a stamp.

No — the original content is untouched and stays selectable; the watermark is drawn as an additional layer on each page. File size grows only trivially (it's just text drawing commands plus one embedded font).