How to add a watermark to a PDF
- Drag one PDF file into the area above, or click it to browse. The total page count appears in the list the moment the file is read.
- Type your watermark text. The default is "CONFIDENTIAL", but you can change it to DRAFT, COPY, DO NOT DISTRIBUTE, your company name — anything up to 60 characters. The button stays disabled while the text box is empty.
- Adjust the placement (diagonal, horizontal center, or bottom), color (gray, red, or blue), opacity (0.08–0.5), and size scale (0.5x–2x) to taste.
- Click Add watermark. The text is stamped on every page and original_watermarked.pdf downloads automatically. Your original file is left untouched.
What makes this different from other PDF watermark sites
Typical online watermark services work by uploading your file to their servers, stamping it there, and sending it back. Think about what kind of document needs a watermark in the first place: contracts, proposals, quotes — files sensitive enough to deserve a CONFIDENTIAL label. Uploading exactly those files to someone else's server, just to mark them confidential, is a strange trade. You have no way to verify when your document is deleted or who can view it during processing.
ThisIsMyPDF's watermark tool never sends your file anywhere. The entire stamping job runs on your own device, using technology built into your browser. That design gives you three advantages:
- Privacy — your file never leaves your device, so there is simply nothing to leak.
- Speed — with no upload or download queue, even documents dozens of pages long finish in seconds.
- No limits — we pay no server costs for processing, so we don't cap file size or how often you use it.
Watermark options in detail
Placement — diagonal, horizontal center, or bottom
Diagonal (center) is the classic choice: the text is tilted to match each page's diagonal angle and spans the whole page, so it survives screenshots and partial crops — the strongest deterrent against unauthorized sharing. Horizontal (center) puts the label straight across the middle of the page for maximum legibility, and Bottom keeps the stamp out of the way of the content, ideal for subtle labels like COPY or a source attribution.
Opacity — balancing visibility and readability
Opacity ranges from 0.08 (barely visible) to 0.5 (bold), with a default of 0.15. A watermark's job is to label the document, not to bury the content under it — so start light enough that the page still reads and prints comfortably, and only turn it up when the label truly needs to dominate.
Size and color
The font size is computed automatically in proportion to each page's diagonal, so the stamp fits sensibly whether the page is Letter, A4, or a small insert — and mixed page sizes within one document each get their own correct size. The scale slider fine-tunes it between 0.5x and 2x. Three colors are available: gray for standard document stamps, red for warnings like DRAFT or VOID, and blue for organizational labels.
When to use it
- Marking outgoing contracts and quotes CONFIDENTIAL to discourage forwarding beyond the intended recipient
- Labeling documents under review as DRAFT so nobody mistakes them for the final version
- Stamping COPY on duplicates of certificates or statements submitted to agencies and banks, so the copy can't pass as an original
- Adding your company or personal name across a proposal or portfolio to deter unauthorized distribution and reuse
- Tagging course materials or handouts with the intended audience (e.g. "Spring 2026 cohort only")
Frequently asked questions
Are my files really never uploaded to a server?
Correct. The entire watermarking job runs inside your browser, on your own computer or phone. The only network activity you might see is a one-time download of a font file from this site when your watermark uses non-English characters — your PDF itself is never sent anywhere. You can verify this in your browser's network tab.
Can the watermark be removed later?
The watermark is drawn directly into the page content rather than added as a separate annotation, so ordinary PDF viewers cannot delete it. Specialized editing tools can still remove it with effort, though — so treat a watermark as a deterrent that discourages unauthorized sharing and labels the document's status, not as unbreakable copy protection. Your original file is left untouched, so keep it as your clean master copy.
Does it support non-English text, like Korean?
Yes. If your watermark contains non-ASCII characters such as Korean, a Unicode font (Noto Sans KR) is fetched once and embedded automatically. Plain English text, numbers, and basic symbols are processed instantly with no font download at all.
Can I watermark a password-protected PDF?
PDFs with an open password cannot be read for security reasons, so a notice is shown instead. Remove the password in a PDF viewer, save a copy, and try again with that file.
What opacity and size should I use?
For documents people still need to read, start with the defaults: a light gray diagonal stamp at around 0.15 opacity. If the label needs to be unmissable — say a DRAFT warning on an internal review copy — raise the opacity to 0.3 or more, or switch the color to red. The size is calculated automatically in proportion to each page's diagonal, and the scale slider fine-tunes it between 0.5x and 2x.