How to Add a Stamp to a PDF

A stamp is the digital version of the rubber block and ink pad: a mark you drop onto a page to say something about the document's state. Approved. Draft. Received 14 March. Confidential. It is a small feature that carries a surprising amount of process weight, because in a lot of organisations the stamp is the signal that a document has passed through a step. This guide covers what a PDF stamp actually is, how to add one in the tools you already have, and where stamps quietly fail to mean what people assume they mean.

A stamp is an annotation, not page content

The important technical fact first: a stamp in a PDF is normally a stamp annotation — an object that sits in a layer above the page rather than inside the page's content stream. That has consequences you will run into eventually:

• It can be moved, resized, or deleted by anyone with an editor, without leaving a trace in the page itself.
• It can be hidden by a viewer that chooses not to render annotations, which is rare but happens with some print drivers and thumbnail generators.
• It does not change the underlying text. Stamping "VOID" across an invoice does not remove the invoice.

If you need the stamp to be permanent, you flatten it — merging the annotation down into the page content so it is no longer a separate, editable object. That is the same operation covered in how to flatten a PDF, and it is the step most people skip.

Adding a stamp in Adobe Acrobat

Acrobat ships the most complete stamp implementation, which is unsurprising given it invented the feature.

1. Open the document and go to Tools → Comment.
2. Click the Stamp tool in the toolbar.
3. Pick from the built-in palettes: Standard Business (Approved, Confidential, Draft, Final, For Comment, Not Approved), Dynamic (which stamps the date, time and your identity automatically), or Sign Here.
4. Click on the page to place it, then drag the corners to resize.

The dynamic stamps are the genuinely useful ones. They are form-driven templates that fill in the current date, time and the user name from your Acrobat identity, which is the difference between a stamp that says "Received" and one that says "Received 2026-07-25 09:14 by A. Okafor". If the process you are supporting cares when something arrived, use dynamic.

You can build your own by putting any PDF into the Stamps folder in your Acrobat user directory, or via Custom Stamps → Create from an image or PDF file. A logo, a firm's received-stamp, a QC mark — all become one-click placements.

Adding a stamp in a browser-based editor

If you do not have Acrobat, most browser-based editors — including our own, Sejda, and PDF24 — approach the same job through images and text boxes rather than a formal stamp annotation. The practical recipe:

1. Make the stamp once as a transparent PNG. Red text on transparency, roughly 800 px wide, is plenty.
2. Place it on the page as an image and scale it down.
3. Position it somewhere that does not sit on top of text you will later need to read or OCR.
4. Export.

The result is visually identical and, because most web editors write the image straight into the page content, it comes out flattened by default — a stamp nobody can drag off. See how to add an image to a PDF for the mechanics, and how to create a transparent signature for PDF for making the transparent PNG cleanly.

Preview on macOS

macOS Preview has no stamp feature by name, but it has everything you need to fake one:

• Markup toolbar → Text for a word like DRAFT, then set the colour to red and the font large in the Font panel.
• Markup toolbar → Shapes for a box around it.
• Edit → Paste for an image stamp copied from Finder.

Preview writes these as annotations, and it will happily let a later reader delete them. To flatten on macOS, print to PDF: File → Print → PDF → Save as PDF bakes the annotations into the page.

Command line, for volume

When you have four hundred documents to stamp, a GUI is the wrong tool. Two approaches worth knowing:

• pdftk background/stamp: pdftk in.pdf stamp overlay.pdf output out.pdf puts a single-page overlay on top of every page. background puts it underneath. This is the fastest path for a fixed stamp applied uniformly. See pdftk introduction.
• qpdf --overlay: qpdf in.pdf --overlay stamp.pdf -- out.pdf, with --repeat options to control which pages get the mark. See qpdf introduction.

Both produce flattened output because the overlay becomes real page content. For anything conditional — stamp only pages matching a rule, or stamp with per-document text — a script using a library like pdf-lib is the honest answer, and it is not much code.

Where stamps mislead people

Three failures come up repeatedly, and all three are about a stamp being taken for something it is not.

A "Confidential" stamp is not protection. It is a label. It sets expectations and may matter legally in a dispute, but it does nothing technical. Anyone can remove it, and anyone can forward the file. If the content genuinely needs protecting, that is encryption or controlled sharing, not ink.

A "Signed" or "Approved" stamp is not a signature. A picture of the word Approved, even with a name and date in it, has no cryptographic binding to the document. It proves nothing about who applied it or whether the file changed afterwards. If the approval needs to hold up, use an actual digital signature — the difference is spelled out in digital signatures vs electronic signatures.

A "VOID" stamp does not void anything. The original text is still there, still extractable, still searchable. If the point is that nobody should be able to read the underlying figures, you want redaction, which removes content rather than covering it.

Practical placement advice

Small details that save re-work:

• Keep stamps off the text block. A stamp over body text ruins OCR of that region and makes the page harder to read on a phone.
• Use the margin or a corner for received/processed marks. Reserve the diagonal-across-the-page treatment for status words like DRAFT, where obscuring the page slightly is the point.
• Watch the print result. A pale red stamp that reads fine on screen can vanish on a mono laser printer. Check with a test print before rolling out a stamp across a process.
• Version your stamp file. If the firm's received-stamp includes a department name that changes, you want one image to update, not four hundred documents.

The short version

Add a stamp with Acrobat's Comment tools if you have it, a transparent PNG placed as an image if you do not, and pdftk/qpdf overlays when the count runs past a few dozen. Then flatten it if it needs to stay put — and remember that a stamp is a statement about a document, never a control over it.