How to Add a Letterhead or Stamp with PDF Overlay

You have an 80-page report and you need to add your corporate letterhead to every page. Or you're stamping "APPROVED" onto every page of a contract, or adding an organization logo to scanned forms. The overlay operation is exactly the tool for this: it places one PDF's content on top of another's.

What an overlay does

You take two PDFs: the main document and the overlay file. The tool draws the overlay file's page content on top of (or beneath) the main document's pages. The result is a new PDF where the two are combined.

The difference from watermark tools is flexibility. A watermark usually takes text or a single image. An overlay uses a complete PDF page — it can contain a vector logo, a multi-color letterhead, border lines, a footer, a QR code, even form fields. You do the design in whatever program you like, save it as PDF, and overlay it.

It also shouldn't be confused with merging: merging arranges pages one after another, while overlay puts them on top of each other.

Step 1: Prepare the overlay file correctly

This step is the most important part of the job and it's where the quality of the result gets determined.

Make the page size the same as the main document's. If your main document is A4, your overlay file should be A4 too. Overlay alignment generally uses the page's bottom left corner as the reference; if the sizes differ, the content shifts. The gap between Letter (216 × 279 mm) and A4 (210 × 297 mm) is big enough to create visible misalignment.

Leave the background transparent. If your overlay file has a white background rectangle, it will completely cover the main document's content when overlaid. Leave the background empty in your design program; use the "don't include background" option when exporting to PDF if there is one.

Use vector if you can. If you place your logo as vector (from SVG or straight out of a design program) rather than as PNG, it stays sharp at every scale and the file size is small. A logo that pixelates when zoomed lowers the quality of the document.

Leave the content area empty. When designing a letterhead, leave the middle of the page — the area where the main document's text will land — empty. Otherwise the letterhead's elements land on top of the text.

If you need transparency, set it now. If you're doing a stamp or watermark-like overlay and you want the text beneath to show through, you have to set the transparency while producing the overlay PDF. Transparency can't be added during the overlay operation.

Step 2: Decide on the layer order

There are two options and the right one depends on the purpose:

Background (underlay): the overlay content is drawn beneath the main document. The main document's text and images stay on top.

Foreground (overlay): the overlay content is drawn on top of the main document. Elements in the overlay can cover the main content.

| Use | Correct choice | Why | |---|---|---| | Letterhead paper | Background | The text should sit on top of the letterhead | | Corporate frame/border | Background | So it doesn't cover the text | | Colored ground | Background | Required | | "APPROVED" stamp | Foreground | The stamp has to be visible | | "DRAFT" watermark | Depends | Foreground if transparent, background if not | | Page number / footer | Foreground | It lands in empty space | | Confidentiality notice band | Foreground | It has to draw attention |

The general rule: if the overlay content mustn't cover the main text, choose background. For letterhead applications background is almost always the right answer.

Step 3: Apply the overlay

Open the PDF overlay tool, upload your main document first and then your overlay file, and choose the layer order. The processing happens in your browser; neither file goes to a server — with corporate letterheads and confidential contracts involved, that's an important difference.

Expect this page-matching behavior:

If the overlay is a single page: the same overlay is applied to every main document page. That's what you want in letterhead and stamp scenarios.

If the overlay has multiple pages: the pages match in sequence — overlay page 1 onto main page 1, page 2 onto page 2. That's useful for corporate templates that want a full letterhead on the first page and a small logo on the rest.

If the overlay is shorter than the main document: it varies by tool — either it repeats from the beginning or the remaining pages are left without an overlay. If you're doing a critical job, verify the behavior first with a 3-4 page test file.

Step 4: Check the result

After downloading, look at these:

The first, middle and last pages. Is the overlay in the right position on all of them? Did the page matching work the way you expected?

Text collisions. Do the letterhead's elements land on top of the text? Check especially on pages with long tables and full-page images.

Pages of different sizes. If the main document contains an A3 drawing, an A4 letterhead will be positioned wrongly on that page. On mixed-size documents check each size separately.

Landscape pages. If the main document contains landscape pages, the letterhead won't fit them in rotated form. In that case you need to separate the landscape pages and process them with a landscape letterhead.

Print preview. Letterheads sit close to the page edges and can land in the border region printers can't print. Check it in the preview with Ctrl+P.

File size. The resources in the overlay file (fonts, logo images) get added to the result. A high-resolution PNG logo doesn't add serious weight to an 80-page file because it's stored once — but if you used a needlessly large image, running compression is still worthwhile.

Real-world scenarios

Corporate letterhead paper. Prepare an A4 letterhead with an empty middle in Word or a design program and save it as PDF. Produce your reports plain, then overlay the letterhead as background. The advantage: when the letterhead changes you don't have to regenerate every document, you just overlay with the new one.

Approval stamp. Prepare the stamp as a single-page PDF with a transparent background and overlay it in the foreground. You determine which corner of the page it lands in through its position in the overlay file.

Numbered copy tracking. If you want to stamp a different number on each copy, you need to prepare a separate overlay file for each number and overlay them individually. That's a method used with legal documents and limited-distribution reports.

Adding a logo to scanned forms. Scanned documents consist of a single large image and can't be edited, but you can overlay on them. You add the logo and organization details in the foreground.

Common mistakes

Leaving a white background in the overlay file. The most common mistake. The entire main document disappears and only the letterhead shows.

Wrong page size. Overlaying a Letter-sized letterhead onto an A4 document creates misalignment.

Confusing foreground and background. If you put the letterhead in the foreground, it covers the text.

Only checking the first page. Page matching behavior may differ from what you expected; check at least three points.

Trying to cover sensitive information with an overlay. An overlay is a visual layer; the content beneath stays in the file and can be extracted as text. Deleting confidential information requires a redaction tool.

In summary

Overlay is the operation of applying a complete PDF page to every page of another PDF, and for jobs like corporate letterheads, stamps and frames it's far more flexible than watermark tools. The key to success lies in preparing the overlay file correctly: the same page size as the main document, a transparent background, an empty content area, and transparency set in advance if needed. The practical rule on layer order — letterheads and frames go to the background, stamps and notices to the foreground. After applying, check the first, middle and last pages; page-matching behavior can vary by tool.