How to Use PDF Merger

Three ways to merge PDFs — the interactive browser app, the REST API, or the MCP tool for AI agents.

Browser App

Interactive PDF Merger

Runs entirely in your browser. No files are ever uploaded to a server — everything happens locally using PDF.js and pdf-lib.

Drag & drop or browse

Load multiple PDFs at once. Files stay on your device — nothing leaves your browser.

Page selection

Click thumbnails or type a range like 2-5, 8, 11-13 to pick exactly which pages you need.

Drag to reorder

Rearrange output pages by dragging them into any order before merging.

Interleave / Insert Rules

Alternate pages from two documents (A1, B1, A2, B2…) or set a custom insertion step.

Full-resolution preview

Click any output page to see it at full resolution before downloading.

One-click download

The merged PDF is assembled locally and saved directly to your device — no waiting.

Step by step

Add your PDFs

Drag files onto the left panel or click anywhere in it to open a file picker. Add as many PDFs as you like — each appears as a collapsible card.

Select pages

Expand a card to see thumbnails. Click to toggle individual pages, or type a selection string like 1-3,7,10-12. Use a reverse range like 10-6 to reverse order.

Send to output

Press the → Output button on a file card to push your selection into the right-hand output panel.

Arrange & preview

Drag output pages into order. Use Insert Rules in the output header to interleave pages from multiple sources automatically.

Merge & download

Click Merge. The PDF is built locally and downloaded immediately.

Page selection syntax

* or emptyAll pages

3Page 3 only

2-5Pages 2, 3, 4, 5

10-6Pages 10, 9, 8, 7, 6 (reverse)

1-3, 8, 11-13Multiple segments, comma-separated

Open PDF Merger

REST API

Server-side Merge API

Upload files first to get UUIDs, then POST a JSON payload describing how to merge them. The response is the merged PDF ready to save or forward.

Step 1

Upload files

POST each PDF to /api/upload — get a UUID filename back for each.

Step 2

Merge

POST to /api/apps/merger with the file UUIDs and your merge options.

Step 1 — Upload a PDF

curl -X POST https://api.docmiral.com/api/upload \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -F "file=@contract.pdf"

# Response:
{
  "status": 1,
  "data": {
    "name": "eee466bd-6813-4aaf-9e48-bc5e2b19d7d3.pdf",
    "size": 204800,
    "extension": ".pdf"
  }
}

Repeat for each file. Use the returned name as the file ID in the merger.

Step 2 — Merge

SimpleAll pages appended in array order

curl -X POST https://api.docmiral.com/api/apps/merger \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "files": [
      {
        "name": "first",
        "file": "eee466bd-6813-4aaf-9e48-bc5e2b19d7d3.pdf",
        "selection": "*"
      },
      {
        "name": "second",
        "file": "a1b2c3d4-1234-5678-abcd-ef1234567890.pdf",
        "selection": "*"
      }
    ]
  }' --output merged.pdf

InterleaveA1 B1 A2 B2 … — also: zip, cross, alternate

curl -X POST https://api.docmiral.com/api/apps/merger \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "files": [
      {
        "name": "doc-a",
        "file": "eee466bd-6813-4aaf-9e48-bc5e2b19d7d3.pdf",
        "selection": "1-5"
      },
      {
        "name": "doc-b",
        "file": "a1b2c3d4-1234-5678-abcd-ef1234567890.pdf",
        "selection": "1-5"
      }
    ],
    "mode": "interleave"
  }' --output merged.pdf

RulePrecise control over page order

curl -X POST https://api.docmiral.com/api/apps/merger \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "files": [
      {
        "name": "file-a",
        "file": "eee466bd-6813-4aaf-9e48-bc5e2b19d7d3.pdf",
        "selection": "2-3,7-10"
      },
      {
        "name": "file-b",
        "file": "a1b2c3d4-1234-5678-abcd-ef1234567890.pdf",
        "selection": "1-5"
      }
    ],
    "mode": "rule",
    "rule": "{file-a}-1-4,{file-b}-2-5"
  }' --output merged.pdf

{file-a}-1-4 picks pages 1–4 of file-a's post-selection pages. Page numbers in rules are 1-based into the selected pages, not the original file.

Mode resolution

mode	rule	result
omitted	empty	simple
omitted	present	rule
simple or interleave	present	400 — remove rule or set mode to "rule"
rule	empty	400 — rule string required

MCP Tool

MCP — AI Agent Integration

The Docmiral MCP server exposes PDF merger as a tool AI agents can call directly. Agents upload files, merge with any selection or rule, and receive the result — all in one conversation turn.

Tool name — MergePDF — appears in tools/list after connecting
Auth — Bearer token in Authorization header (JWT or OAuth APIAccessToken)
Binary response — Merged PDF returned as base64 inside the MCP content block
Full parity — All modes (simple, interleave, rule) work identically to the REST API

Connect (Claude Desktop)

// claude_desktop_config.json
{
  "mcpServers": {
    "docmiral": {
      "url": "https://api.docmiral.com/api/mcp",
      "headers": {
        "Authorization": "Bearer YOUR_TOKEN"
      }
    }
  }
}

Initialize

POST https://api.docmiral.com/api/mcp
Authorization: Bearer YOUR_TOKEN

{ "jsonrpc": "2.0", "id": 1, "method": "initialize", "params": {} }

Call MergePDF

{
  "jsonrpc": "2.0",
  "id": 3,
  "method": "tools/call",
  "params": {
    "name": "MergePDF",
    "arguments": {
      "body": {
        "files": [
          {
            "name": "file-a",
            "file": "eee466bd-6813-4aaf-9e48-bc5e2b19d7d3.pdf",
            "selection": "2-3,7-10"
          },
          {
            "name": "file-b",
            "file": "a1b2c3d4-1234-5678-abcd-ef1234567890.pdf",
            "selection": "1-5"
          }
        ],
        "mode": "rule",
        "rule": "{file-a}-1-4,{file-b}-2-5"
      }
    }
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 3,
  "result": {
    "content": [{
      "type": "text",
      "text": "{
        "type": "binary",
        "content_type": "application/pdf",
        "filename": "merged.pdf",
        "data_base64": "JVBERi0xLjQK...",
        "size": 42318
      }"
    }]
  }
}

Decode data_base64 to get the raw PDF bytes. File UUIDs must come from a prior UploadFile tool call.

Typical agent workflow

1Call UploadFile for each PDF — collect the UUID filenames returned.
2Call MergePDF with the UUIDs, selection strings, and the desired mode or rule.
3Decode data_base64 from the response and save or forward the merged PDF.

Ready to merge?

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Open PDF Merger