Merge PDF Overlay
Merge & Split → Merge PDF Overlay
The Merge PDF Overlay API overlays one PDF on top of another. You send baseDocContent and baseDocName (base PDF), layerDocContent and layerDocName (layer PDF), and optionally async. The API returns a single PDF with the layer overlaid on the base. Use the tester below to try it; more details are in the sections that follow.
Try the Merge PDF Overlay API
Endpoint: POST /api/v2/MergeOverlay · Required: api-key, baseDocContent, baseDocName, layerDocContent, layerDocName
Use the form below to send your API key, base PDF (Base64), and layer PDF (Base64). The response is one PDF with the overlay applied. No code required—fill the fields and click Send request.
Overview, parameters, and use cases
- Overview
- Parameters
- Use cases
What is Merge PDF Overlay?
This endpoint overlays a layer PDF on top of a base PDF. You provide baseDocContent and baseDocName (base PDF) and layerDocContent and layerDocName (layer PDF). The API combines them into one PDF with the layer overlaid on the base. Use it for watermarks, letterheads, or combining form and content.
Key features
- Base and layer – Base PDF (first layer), layer PDF (overlaid on top).
- Single output – One PDF with both combined.
- Async – Use async for large PDFs.
Use when overlaying a letterhead, watermark, or form on content. For concatenating PDFs use Merge Multiple PDF Files.
API parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
| api-key | string | Yes | Your PDF4me API key, Base64 encoded. Get it from the dashboard. |
| baseDocContent | base64 | Yes | Base PDF content (Base64). |
| baseDocName | string | Yes | Base PDF file name (e.g. base.pdf). |
| layerDocContent | base64 | Yes | Layer PDF content (Base64) to overlay. |
| layerDocName | string | Yes | Layer PDF file name (e.g. layer.pdf). |
| async | boolean | No | Enable asynchronous processing. |
When to use Merge PDF Overlay
- Letterheads – Overlay a letterhead PDF on content.
- Watermarks or forms – Combine a form or watermark layer with a content PDF.
- Pre-printed layout – Overlay content onto a template PDF.
For request/response schemas and code samples, see Merge Overlay in the PDF4me API docs.
Prerequisites
Before using this endpoint, make sure you have:
- A valid PDF4me API key (Get your API Key)
- A base PDF file in Base64 format
- A layer PDF file in Base64 format to overlay
Response Format
The API returns a PDF file with the layer PDF overlaid on top of the base PDF.