PDF Watermark

How to add a PDF text watermark

1. Choose one ordinary unencrypted PDF, up to 25 MiB and 300 pages. Its bytes are parsed locally; its extension alone is not trusted.
2. Edit the visible DRAFT example. Use 1–60 characters on one line, then choose center or a corner, regular or bold text, color, opacity and font size.
3. Use All physical pages or ranges such as 1-3, 7. Numbers start at 1; duplicates are removed and pages stay in their original order.
4. Select a preview page and press Update preview after changing settings. An outdated preview is labelled explicitly and is not evidence of current placement.
5. Press Generate watermarked PDF. Every selected page is checked before any final file is offered. Download the separate original-watermarked.pdf copy and keep your source.

Worked example

For a ten-page review document, enter CONFIDENTIAL, choose pages 1-3, 7, center placement, −35°, 60 pt and 20% opacity. Four pages receive one new text overlay each; the other six receive none. The output still has ten pages in the same order.

With Fit text to page enabled, a narrow page may use a smaller effective size than 60 pt. The preview reports that page's actual size. Fit never enlarges text, and settings that require less than 6 pt are rejected instead of producing an unreadable mark.

Placement, angles and fitting

Angles use the visible screen frame: positive angles turn clockwise; −35° rises from left to right. Existing 90°/180°/270° PDF rotation does not change the apparent watermark angle. Placement accounts for nonzero MediaBox/CropBox origins and their visible intersection.

The bundled font's actual glyph outlines determine the text bounds, including accents and descenders. The mark rotates about those bounds' center. Corner placement anchors the rotated bounds inside the inset; center placement centers them. The 3–40 mm inset also reserves a fit margin for center placement.

Font size starts at 60 pt and accepts 12–144 pt; fitted output may be as small as 6 pt. Fit scales both dimensions uniformly, down only. Without Fit, a mark that would clip is an error. All invalid selected pages are grouped in an actionable error before export; there is no partial-success download.

Text, font and opacity

Liberation Sans regular and bold are bundled locally with their license. This release accepts Basic Latin and Latin-1 letters, including Å, Ä, Ö and é; ordinary punctuation, smart quotes, dashes, ellipsis, euro and trademark symbols. Emoji, combining-mark sequences, non-Latin scripts, line breaks and invisible/control characters are rejected, not replaced silently.

Opacity ranges from 5% to 100%, defaulting to 20%. The overlay is real PDF text with transparency—not an opaque rectangle or a picture of the original page. It can overlap existing content and may be difficult to read over busy backgrounds. A bounded raster preview is for review only; export does not rasterize the original pages.

Supported documents and honest limitations

Encrypted/password-protected, corrupt PDFs, detected digital-signature fields, interactive forms and document-level signature/permission data are rejected. Modification can invalidate signatures and PDF/A conformance; this tool does not certify preservation of tags, bookmarks, attachments or every annotation feature. It is not a PDF sanitizer. Review the separate copy in your usual PDF viewer.

Nonstandard UserUnit scaling, invalid/extreme page boxes and rotations that are not quarter-turns are unsupported for watermark placement. A PDF within the size/page limits can still exhaust browser memory. Final output is limited to 100 MiB; previews render one page at a time, at most 512 px per edge.

Cancel terminates local processing and discards obsolete replies. A canceled or failed export is never offered as a completed PDF. Clear / Reset offers memory-only Undo, including retained valid preview/downloads. Accepting a new PDF releases the cleared snapshot. Editing export settings invalidates the old download immediately while keeping the prior preview visibly outdated.

No watermark text, PDF bytes or filenames are placed in URLs, analytics, logs or persistent browser storage. Only bundled fonts, application assets and the site's separately described advertising/consent services make network requests.

A watermark does not secure a PDF

This is visible embedded content, not encryption, redaction, a digital signature, copy protection or a guarantee against removal, editing or disclosure. Logo/image watermarks, invisible marks and watermark removal are not included. PDF page numbering and image watermarking remain separate planned tools, not features of this release.