A PDF stamp is a visual mark placed on a document page — "APPROVED", "CONFIDENTIAL", "DRAFT", "RECEIVED", or a custom image like a company seal. Stamps are used to indicate a document's status, restrict its use, or mark it as reviewed. Unlike a watermark, which typically appears on every page, a stamp is usually placed on specific pages at a specific location.
Stamp vs Watermark: What's the Difference?
In PDF terminology, a stamp is an annotation placed on a specific page — it's a discrete object that can be moved, resized, or deleted. A Watermark PDF is typically applied to every page as a background or foreground overlay using the watermark tool, which applies it globally rather than page by page.
In practice, people use both terms loosely. A "CONFIDENTIAL" mark placed on the first page might be called a stamp or a watermark depending on who's using the term. The distinction matters mainly when choosing which tool to use: the Stamp tool for individual page annotations, the Watermark tool for document-wide background marks.
Adding a Stamp in Adobe Acrobat
Adobe Acrobat Reader and Acrobat Pro both include a Stamp tool in the comment/annotation panel. Acrobat comes with a library of pre-built stamps — standard business stamps like APPROVED, REJECTED, DRAFT, CONFIDENTIAL, FOR PUBLIC RELEASE, and date stamps. To use them:
- Go to Tools > Comment, then select the Stamp tool from the toolbar
- Choose a stamp category and select the stamp you want — Standard Business, Dynamic (auto-fills with date and username), or Sign Here
- Click on the page where you want the stamp placed
- Resize and reposition by dragging — the stamp is an annotation object that can be moved until you flatten the document
Dynamic stamps are particularly useful for workflow processes — they automatically insert the current date, time, and the user's name when applied, creating a record of who stamped the document and when.
Creating a Custom Stamp
Standard stamps cover common needs, but custom stamps let you use your company logo, a specific legal notice, or any text or image combination you need. In Acrobat Pro, create a custom stamp from:
- A PDF file: Tools > Comment > Stamp > Custom Stamps > Create, then select a PDF containing your stamp design. Each page of the PDF becomes a separate custom stamp option.
- An image file: convert your stamp image (PNG, JPEG) to a one-page PDF first, then import it as a custom stamp. Use a PNG with transparent background for a stamp that sits cleanly over the document without a white box.
Adding a Stamp Without Adobe Acrobat
For a simple stamp effect without Acrobat, the image overlay approach works in any PDF Editor that supports image insertion. Add a PNG image of the stamp text (created in any design tool) on top of the relevant page, position it, and save. WukongPDF at www.wukongpdf.com supports image insertion — upload the PDF, add the stamp image, download the result.
For text-based stamps, a text box with a colored border achieves a similar effect — add a text box with "DRAFT" in red bold text, position it diagonally if needed, and the visual result is a recognizable stamp. This approach is less polished than a proper stamp annotation but requires no specialized software.
Making a Stamp Permanent
A stamp placed as an annotation is still a separate layer — anyone with editing capability can select and delete it. To make it permanent and part of the page, flatten the document after stamping. The stamp becomes part of the page image and can no longer be separated from the content.
Flatten by printing to PDF (File > Print > Save as PDF) — this bakes all annotations including stamps into the page. Keep the pre-flatten version as a working copy if you might need to adjust the stamp later. The flattened version is the final, distributable copy with the stamp permanently applied. For a document you're distributing with a "CONFIDENTIAL" or "APPROVED" stamp, flattening before sending ensures the recipient receives the stamp as a permanent part of the document rather than a removable annotation.