---
title: "PDF flatten API"
canonical_url: "https://www.nutrient.io/guides/dws-processor/tools-and-api/pdf-flatten-api/"
md_url: "https://www.nutrient.io/guides/dws-processor/tools-and-api/pdf-flatten-api.md"
last_updated: "2026-07-06T00:00:00.000Z"
description: "Flatten PDF annotations and form field appearances into page content using Nutrient DWS Processor API. Make annotations non-editable before sharing, archiving, or signing."
---

# PDF flatten API

Use the PDF flatten API to turn annotations into regular PDF page content. Flattening makes annotations non-editable, so use it when preparing a document for sharing, archiving, printing, or signing.

The [`/build` endpoint](https://www.nutrient.io/api/reference/public/#tag/Document-Editing/operation/build-document) handles flattening. Add the source PDF as a `parts` item, and add a `flatten` action.

For signup, pricing, and task-level examples, refer to the [flatten PDF API task page](https://www.nutrient.io/api/flatten-pdf-api/).

## Flatten all annotations

The following example flattens all annotations in `document.pdf` and writes the output to `result.pdf`:

### Shell

### Shell (Windows)

### Java

### C#

### JavaScript

### Python

### PHP

### HTTP

## Flatten a PDF from a URL

For remotely hosted source files, send a JSON request and pass the source URL in `parts[].file.url`. Use this instructions object:

```json

{
  "parts": [
    {
      "file": {
        "url": "https://example.com/annotated-document.pdf"
      }
    }
  ],
  "actions": [
    {
      "type": "flatten"
    }
  ]
}

```

### Shell

Run this request to flatten a PDF from a URL:

```bash

curl -X POST https://api.nutrient.io/build \
  -H "Authorization: Bearer $NUTRIENT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "parts": [
      {
        "file": {
          "url": "https://example.com/annotated-document.pdf"
        }
      }
    ],
    "actions": [
      {
        "type": "flatten"
      }
    ]
  }' \
  -o result.pdf

```

## Flatten selected annotations

By default, the `flatten` action flattens all annotations. To flatten only specific annotations, pass their IDs in `annotationIds`.

Annotation IDs can be annotation IDs or PDF object IDs. Use this option when you want to make only some annotations permanent while leaving the rest editable.

Use this instructions object to flatten selected annotations:

```json

{
  "parts": [
    {
      "file": "document"
    }
  ],
  "actions": [
    {
      "type": "flatten",
      "annotationIds": [
        "01H9Z0Y6J3V7R6W8K9M0N1P2Q3",
        42
      ]
    }
  ]
}

```

## Flatten after importing annotations

The `/build` endpoint can import annotations and then flatten them in the same request. Actions run in the order specified in the `actions` array.

The following example imports annotations from XML Forms Data Format (XFDF) and then flattens the result:

```json

{
  "parts": [
    {
      "file": "document"
    }
  ],
  "actions": [
    {
      "type": "applyXfdf",
      "file": "annotations"
    },
    {
      "type": "flatten"
    }
  ]
}

```

You can use the same pattern with Instant JSON by using the `applyInstantJson` action before `flatten`.

## Flatten selected pages

The `flatten` action applies to the assembled PDF in the request. To flatten only a range of pages, first extract the pages you want to flatten with `parts[].pages`, flatten that output, and then merge it back into the final document if needed.

The following example extracts pages zero through two and flattens only those extracted pages in the output PDF:

```json

{
  "parts": [
    {
      "file": "document",
      "pages": {
        "start": 0,
        "end": 2
      }
    }
  ],
  "actions": [
    {
      "type": "flatten"
    }
  ]
}

```

To create a final PDF that contains both flattened and editable sections, process the flattened section first, and then merge it with the other page ranges. For merge workflows, refer to the [PDF merge API](https://www.nutrient.io/guides/dws-processor/tools-and-api/pdf-merge-api.md) guide.

## Flatten password-protected PDFs

If the source PDF is password-protected, include the password on the part. Use this instructions object:

```json

{
  "parts": [
    {
      "file": "protected_document",
      "password": "document-password"
    }
  ],
  "actions": [
    {
      "type": "flatten"
    }
  ]
}

```

Nutrient DWS Processor API uses the password only to open the source document for processing. To set a password on the output PDF, configure `output.user_password`, `output.owner_password`, and `output.user_permissions`.

## Combine flattening with other actions

Flattening is usually a finalization step. Run content-changing operations such as merging, page extraction, annotation import, form filling, rotation, and watermarking before flattening when the output should no longer be editable.

The following example merges two PDFs, adds a watermark, and then flattens annotations into the final output:

```json

{
  "parts": [
    {
      "file": "first_half"
    },
    {
      "file": "second_half"
    }
  ],
  "actions": [
    {
      "type": "watermark",
      "text": "FINAL",
      "width": "50%",
      "height": "20%",
      "opacity": 0.3,
      "rotation": 45
    },
    {
      "type": "flatten"
    }
  ]
}

```

For workflows that include signing, flatten the document before signing the final PDF.

## Reference

A PDF flatten request uses the Build API `actions` array with a `flatten` action:

```typescript

type FlattenAction = {
  type: "flatten",

  // Optional annotation IDs or PDF object IDs to flatten.
  // If omitted, all annotations are flattened.
  annotationIds?: Array<string | number>,
};

type FilePart = {
  // Multipart field name, or a remote URL object.
  file: string | { url: string },

  // Optional password for encrypted input PDFs.
  password?: string,

  // Optional page range to extract before flattening.
  pages?: {
    start?: number,
    end?: number,
  },
};

type BuildInstructions = {
  parts: FilePart[],
  actions: FlattenAction[],
  output?: {
    type?: "pdf",
  },
};

```

## Related API reference operations

- Refer to the [build document endpoint](https://www.nutrient.io/api/reference/public/#tag/Document-Editing/operation/build-document) API reference for flattening annotations, selecting page ranges, importing annotations, and applying follow-up actions in a single request.

## Related guides

- Refer to the [PDF merge API](https://www.nutrient.io/guides/dws-processor/tools-and-api/pdf-merge-api.md) guide.

- Refer to the [PDF split API](https://www.nutrient.io/guides/dws-processor/tools-and-api/pdf-split-api.md) guide.

- Refer to the [PDF rotate API](https://www.nutrient.io/guides/dws-processor/tools-and-api/pdf-rotate-api.md) guide.

- Refer to the [PDF watermark API](https://www.nutrient.io/guides/dws-processor/tools-and-api/pdf-watermark-api.md) guide.

- Refer to the [PDF security API](https://www.nutrient.io/guides/dws-processor/tools-and-api/pdf-security-api.md) guide.

- Refer to the [tools and APIs](https://www.nutrient.io/guides/dws-processor/tools-and-api.md) guide.
---

## Related pages

- [Image-to-PDF API](/guides/dws-processor/tools-and-api/image-to-pdf-api.md)
- [Document-to-image API](/guides/dws-processor/tools-and-api/document-to-image-api.md)
- [DOCX templating API](/guides/dws-processor/tools-and-api/docx-templating-api.md)
- [Import XFDF annotations API](/guides/dws-processor/tools-and-api/import-xfdf-annotations-api.md)
- [Analyze Build API](/guides/dws-processor/tools-and-api/analyze-build-api.md)
- [Office-to-PDF API](/guides/dws-processor/tools-and-api/office-to-pdf-api.md)
- [Tools and APIs](/guides/dws-processor/tools-and-api.md)
- [Import Instant JSON API](/guides/dws-processor/tools-and-api/import-instant-json-api.md)
- [Markdown-to-PDF API](/guides/dws-processor/tools-and-api/markdown-to-pdf-api.md)
- [PDF linearization API](/guides/dws-processor/tools-and-api/pdf-linearization-api.md)
- [PDF merge API](/guides/dws-processor/tools-and-api/pdf-merge-api.md)
- [PDF digital signature API](/guides/dws-processor/tools-and-api/pdf-digital-signature-api.md)
- [PDF optimization API](/guides/dws-processor/tools-and-api/pdf-optimization-api.md)
- [PDF form filling API](/guides/dws-processor/tools-and-api/pdf-form-filling-api.md)
- [PDF security API](/guides/dws-processor/tools-and-api/pdf-security-api.md)
- [PDF rotate API](/guides/dws-processor/tools-and-api/pdf-rotate-api.md)
- [PDF page manipulation API](/guides/dws-processor/tools-and-api/pdf-page-manipulation-api.md)
- [PDF-to-image API](/guides/dws-processor/tools-and-api/pdf-to-image-api.md)
- [PDF split API](/guides/dws-processor/tools-and-api/pdf-split-api.md)
- [PDF watermark API](/guides/dws-processor/tools-and-api/pdf-watermark-api.md)
- [PDF OCR API](/guides/dws-processor/tools-and-api/pdf-ocr-api.md)
- [PDF-to-HTML API](/guides/dws-processor/tools-and-api/pdf-to-html-api.md)
- [PDF-to-PDF/A API](/guides/dws-processor/tools-and-api/pdf-to-pdfa-api.md)
- [PDF generator API](/guides/dws-processor/tools-and-api/pdf-generator-api.md)
- [PDF/UA auto-tagging API](/guides/dws-processor/tools-and-api/pdfua-api.md)
- [PDF-to-Markdown API](/guides/dws-processor/tools-and-api/pdf-to-markdown-api.md)
- [PDF-to-Office API](/guides/dws-processor/tools-and-api/pdf-to-office-api.md)
- [Redaction API](/guides/dws-processor/tools-and-api/redaction-api.md)