Yes — adding a text watermark ("DRAFT", "CONFIDENTIAL", your company name) to a PDF is available in free tools and doesn't require Acrobat. Image watermarks are also possible. The options depend slightly on what kind of watermark you need and how it should behave.
Text Watermarks: The Most Common Use Case
A text watermark — diagonal "DRAFT" across every page, "CONFIDENTIAL" in faded text, your name or company across the document — is the most frequently needed watermark type. Browser-based PDF Editor tools handle this: upload the PDF, specify the watermark text, choose placement (center, diagonal, corner), adjust opacity so it's visible but doesn't obscure content, and download.
WukongPDF includes a watermark tool that applies text across all pages in a single operation. Set the text, font size, and opacity, position it, and the watermark appears on every page of the output PDF. This handles the "mark all pages consistently" requirement that makes manual watermarking so tedious.
Image Watermarks: Logos and Signatures
An image watermark — a semi-transparent logo in the corner of every page, a stamp image on specific pages — requires a tool that supports image overlays. Most PDF editing tools that support text watermarks also support image watermarks: upload the image (typically PNG with a transparent background), set the opacity and position, and apply.
For logo watermarks, use a PNG with a transparent background at a reduced opacity (20-40% opacity is typically readable but not distracting). A pure white background on the logo image will show as a white box over the document content, which is rarely what you want.
On Mac Without Any Extra Tools
Preview on Mac can add simple watermarks using the text annotation tool. Open the PDF, select the text tool in Markup, type your watermark text, resize and position it, adjust the color and opacity. For a single page this works quickly. For multi-page documents, you'd need to repeat this on every page, which makes it less practical for anything beyond a few pages.
For multi-page documents on Mac, a browser-based tool that applies the watermark to all pages at once is significantly faster than the Preview approach.
Watermarks That Persist vs. Watermarks That Can Be Removed
There's an important distinction between a watermark that's flattened into the page content and one that's added as a separate annotation layer. A flattened watermark is part of the visual content of each page — it's as permanent as the text and images. Removing it requires image editing of each page.
An annotation-layer watermark is added as an overlay that, in principle, can be removed by editing the PDF's annotation structure. For "DRAFT" or "CONFIDENTIAL" labels on documents you'll finalize later, this is often fine — you remove the watermark when finalizing. For watermarks intended as permanent branding or protection, a flattened watermark is more robust.
Most free browser watermark tools produce flattened watermarks because they rebuild the page during processing. This is generally what you want for persistence. If you specifically need a removable watermark (for a review workflow where the watermark comes off when the document is approved), confirm how the tool handles this before processing a large batch.
Personalizing Watermarks for Each Recipient
Personalizing watermarks — embedding the recipient's name or email in the document so you can trace unauthorized redistribution back to the source — requires either batch watermarking software or manual processing of each copy. For small volumes (5-10 recipients), processing each copy individually through a browser tool takes a few minutes per document and creates a traceable distribution record.