Can I add a diagonal watermark to a PDF?

Yes. Use the angle slider to set the text rotation — 45 degrees gives the classic diagonal watermark effect used on draft and confidential documents. Combine the diagonal angle with the 'Center' position option to place the watermark across the middle of each page for maximum visibility without obscuring the document margins.

Will the watermark be permanent?

The watermark is embedded directly into the PDF page content and cannot be removed by simply selecting and deleting it in a standard PDF reader. It requires a PDF editing tool like Adobe Acrobat to remove. For the highest level of tamper resistance, flatten the PDF after watermarking using a separate PDF editor, which merges all layers into a single non-editable layer.

What fonts are available?

This tool uses Helvetica Bold, one of the 14 standard built-in PDF fonts that are guaranteed to render correctly in every PDF viewer without requiring font embedding. Using a standard font keeps the output file size small. Custom fonts would require the full font data to be embedded in the PDF, which can add hundreds of kilobytes to the file size.

PDF Watermark

Add text watermarks to PDF documents — free, private, in-browser

Watermarking PDFs protects your documents from unauthorized distribution, marks drafts clearly before final approval, and identifies confidential materials. This free tool embeds a customizable text watermark directly into every page of your PDF using pdf-lib — no server upload, no account, and no per-file charge. The watermark becomes a permanent part of the PDF structure, so it cannot be easily removed by simply deleting a layer in a standard PDF viewer.

Watermark customization options

This tool gives you full control over how the watermark appears. Text content can be anything — "CONFIDENTIAL", "DRAFT", your company name, "FOR REVIEW ONLY", or a custom phrase. Position options include center (most common), diagonal across the page, top-right corner, bottom-center footer, and more. Opacity controls how visible the watermark is — a low opacity (15–25%) creates a subtle background mark that doesn't obscure the content; higher opacity (60–80%) creates an obvious mark that signals the document status clearly.

When to use PDF watermarks

Common use cases include marking draft contracts "DRAFT" before sending for review, adding "CONFIDENTIAL" to sensitive business documents before sharing with external parties, watermarking portfolio work with your name or website to deter copyright theft, marking e-books or course materials with a buyer's name or order number to deter unauthorized sharing, and adding "FOR INTERNAL USE ONLY" to HR or financial documents shared via email.

Diagonal vs horizontal watermarks

A diagonal watermark at 45° is the most common style because it is visible across the widest variety of page content — it won't be hidden by text blocks or images aligned to the page margins. Horizontal watermarks in the footer or header are less obtrusive and work well for brand attribution rather than security marking. Center watermarks at high opacity are used when the goal is to make the document clearly unusable without authorization, such as on sample preview pages of paid content.

Privacy — your documents stay on your device

PDF files often contain sensitive business, legal, or financial information. All watermarking operations in this tool run entirely in your browser using JavaScript. Your PDF is loaded into browser memory, processed with pdf-lib, and written back as a downloadable file. Nothing is ever sent to a server. This makes the tool suitable for confidential contracts, medical documents, HR records, and legal filings.