How to Overlay Two PDF Files for Free Online (2025)
Table of Contents
- What Is PDF Overlay?
- Common Use Cases
- Step-by-Step: Overlay Two PDFs Free Online
- Overlay vs. Merge — What's the Difference?
- FAQ
What Is PDF Overlay? {#what-is-pdf-overlay}
PDF overlay places the content of one PDF directly on top of another. Both documents occupy the same physical page area, with one rendered transparently over the other.
The result: a single PDF where two layers of content appear simultaneously on each page.
Common Use Cases {#common-use-cases}
Adding a letterhead to an existing document You have a company letterhead PDF (logo, address, header/footer design) and a content PDF. Overlay the letterhead onto the content to produce a branded document without recreating everything in Word.
Combining a form template with filled data You have a blank form template and a separate PDF with the data positioned to match. Overlay them to produce a filled form.
Watermarking entire documents For more customizable watermarks than the Watermark tool offers, create a separate single-page watermark PDF and overlay it onto your document.
Adding legal disclaimers or stamps Create a PDF with just a "FOR REVIEW ONLY" text layer, then overlay it onto any document you distribute for review.
Step-by-Step: Overlay Two PDFs Free Online {#step-by-step-overlay-pdfs}
Step 1 — Open the Overlay tool
Go to PDF724 PDF Overlay. No account or installation required.
Step 2 — Upload the base PDF (bottom layer)
This is your main document — the one that will show through. Click Select Base PDF.
Step 3 — Upload the overlay PDF (top layer)
This is the layer that will be placed on top. Click Select Overlay PDF. This could be a letterhead, watermark page, or stamp template.
Step 4 — Adjust overlay opacity
Use the opacity slider to set how transparent the top layer should be:
- 100% opacity — Top layer is fully visible, may obscure base content
- 50% opacity — Both layers show through equally
- 20–30% opacity — Subtle background effect, base content dominates
For letterheads and stamps, 100% opacity usually works best. For watermarks, 15–25% keeps them visible without obscuring content.
Step 5 — Create and download
Click Create Overlay PDF. Download the result.
Overlay vs. Merge — What's the Difference? {#overlay-vs-merge}
| Operation | Result | Use When |
|---|---|---|
| Overlay | Two PDFs stacked on the same pages | Both documents cover the same content area |
| Merge | Two PDFs appended sequentially | Documents have separate, sequential pages |
Example: A letterhead + a 5-page report should be overlaid — the letterhead appears on all 5 pages. Merging would put the letterhead as page 1 and the report as pages 2–6.
FAQ
Does the overlay work if the two PDFs have different page sizes? The overlay scales the top-layer page to match the base page dimensions. If they have very different proportions (portrait vs. landscape), the overlay may not align perfectly. For best results, use PDFs with the same page size.
What if my base PDF has 10 pages but my overlay PDF has only 1 page? The single overlay page is applied to all 10 base pages.
What if both PDFs have a different number of pages? The tool uses the page count of the longer document. Shorter document pages are repeated where needed.
Can I overlay an image instead of a PDF? Convert your image to a single-page PDF first using the Images to PDF tool, then use that as the overlay.
Does the file get uploaded to a server? No. Both PDFs are processed entirely in your browser using pdf-lib. Files never leave your device.