> ## Documentation Index > Fetch the complete documentation index at: https://developers.gonitro.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Flatten > Flatten PDF document The `Flatten` method of the Transformations endpoint lets you flatten interactive or layered elements in a PDF, converting them into static, non-editable content. Flattening merges all layers and elements into the base page content. This process is irreversible, interactive features cannot be restored, and elements cannot be edited or removed without specialized editing tools. Elements that can be flattened include: * Form fields (text boxes, checkboxes, radio buttons, dropdown menus) * Annotations (comments, highlights, sticky notes, markup) * Digital signatures and signature fields * Layers and optional content groups * Transparencies and blend modes ### Output File Format The endpoint can return output either as JSON or as a binary file. The format depends on the `Accept` header (details below), which defaults to application/json. ### Processing When requesting JSON, you can run the operation synchronously or asynchronously. This is determined by the `Prefer` header (details below). * In sync mode, the response includes a URL pointing to the processed file. * In async mode, the request creates a Job, and the response contains the Job ID and status so you can track progress. Binary (octet-stream) responses are only available for synchronous operations. ### Custom File Delivery The endpoint supports custom file-delivery destinations through the optional delivery parameter. You can provide an upload target, such as your own PUT endpoint or a pre-signed S3 URL, and Nitro will upload the resulting file there. This works for both synchronous and asynchronous processing. * ### Sync delivery In synchronous calls, the [delivery](#body-delivery) parameter lets you direct Nitro to upload the output file to a custom URL endpoint or a pre-signed URL (e.g S3), by providing an upload url in the `uploadResultTo` or `uploadResultsTo` properties. #### Custom endpoint If implementing the upload endpoint by yourself, make sure your code or middleware configuration accepts requests without content-type headers. #### S3 delivery If you are using S3 to manage delivery uploads, follow this [AWS documentation](https://docs.aws.amazon.com/AmazonS3/latest/userguide/PresignedUrlUploadObject.html) to generate a pre-signed PUT URL. If using the AWS provided Python script, omit the `Content-Type` in Params to get the pre-signed url. For example: ```python theme={null} url = generate_presigned_url( s3_client, "put_object", { "Bucket": args.bucket, "Key": args.key, # Content-Type: "application/octet-stream" => Omit! }, 1000) ``` * ### Async delivery In asynchronous flows, you can also provide a custom URL or pre-signed S3 object via `uploadResultTo` or `uploadResultsTo`, to upload your file(s) once the Job is done processing. #### Callback For asynchronous processing, you can also include a [callback](#body-delivery-callback) URL within the delivery parameter. This callback is a POST endpoint that Nitro will call once the Job is created and running, providing details about the file-processing job. Example of Nitro’s callback request body: ```json theme={null} { "jobID": "babe2aa7-9b5d-4eb2-a679-5fc12cf0a490", "location": "https://api.gonitro.dev/jobs/babe2aa7-9b5d-4eb2-a679-5fc12cf0a490" } ``` #### Response behavior Matrix This matrix shows the expected response behavior based on content type, sync/async mode, and custom file-delivery settings. | | **JSON (`application/json`)** | **Binary (`application/octet-stream`)** | | ---------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------- | | **Synchronous** | Returns a JSON object with a file(s) URL(s). | Returns the processed file directly as binary. | | **Asynchronous (`respond-async`)** | Returns a JSON object with a Job ID and status. | Async preference ignored, returns sync binary. | | **Synchronous delivery** | File delivered to custom endpoint / Bucket, returns success confirmation. | N/A | | **Asynchronous delivery** | Returns a JSON object with a Job ID and status. The file(s) will be uploaded to the provided PUT endpoint / S3 Bucket at the end of process. If `callback` url is provided, Nitro will notify the endpoint with a JOB ID and location. | N/A | #### Limits The Platform API has the following limits: * File size: Maximum of 25 MB per request. This applies to single-file and multi-file requests. * Page count: Maximum of 250 pages per individual document. This applies to single-file and multi-file requests. Multiple documents may exceed 250 pages in total. * Retention time: Inputs and outputs are deleted approximately 15 minutes after the operation completes. ### Request ## OpenAPI ````yaml flatten POST /transformations openapi: 3.0.3 info: title: Nitro API - Document Intelligence Platform description: >- Consolidated API for document intelligence operations including conversions, extractions, transformations, and job management. **Supported Operations:** - **Conversions**: PDF ↔ MS Office, Images ↔ PDF, Various formats to PDF - **Extractions**: Text extraction, PII detection, Bounding box extraction, PDF properties - **Transformations**: Rotate, Split, Merge, Flatten, Compress, Password protection, Redaction - **Jobs**: Asynchronous processing with status monitoring and result retrieval **Global Limits:** - Maximum file size: 25MB - Maximum number of pages: 200 version: 1.0.0 contact: name: Nitro API Support url: https://help.gonitro.com/support servers: - url: https://api.gonitro.dev description: API server security: [] tags: - name: Conversions description: >- Document format conversion operations including PDF to/from MS Office, images, and various other formats - name: Extractions description: >- Data extraction operations for text, metadata, PII detection, and bounding box information - name: Transformations description: >- PDF transformation operations including rotation, splitting, merging, compression, protection, and redaction - name: Jobs description: >- Asynchronous job management for monitoring, retrieving results, and canceling long-running operations paths: /transformations: post: tags: - Transformations summary: Flatten PDF description: Flatten PDF document parameters: - name: Accept in: header schema: $ref: '#/components/schemas/AcceptHeader' - name: Prefer in: header schema: $ref: '#/components/schemas/PreferHeader' requestBody: required: true content: multipart/form-data: schema: type: object properties: method: type: string description: 'The Transformations'' endpoint method: `flatten`' default: flatten enum: - flatten file: $ref: '#/components/schemas/FileUpload' delivery: $ref: '#/components/schemas/DeliverySingleFileOut' required: - method - file responses: '200': description: >- Returns either JSON or binary output depending on the Accept header (defaults to JSON). JSON responses include a file URL for synchronous tasks or a job status for asynchronous tasks. content: application/json: schema: oneOf: - $ref: '#/components/schemas/PlatformOperationFileResult' - $ref: '#/components/schemas/AsyncJobResponse' application/octet-stream: schema: type: string format: binary '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '404': $ref: '#/components/responses/NotFound' '413': $ref: '#/components/responses/ContentTooLarge' '422': $ref: '#/components/responses/UnprocessableEntity' '500': $ref: '#/components/responses/InternalServerError' security: - BearerAuth: [] components: schemas: AcceptHeader: type: string enum: - application/json - application/octet-stream - '*/*' default: '*/*' description: >- Controls response format and behavior. See endpoint description above for detailed response combinations. - `application/json`: Returns JSON response with operation result - `application/octet-stream`: Returns binary file content - `*/*`: Defaults to JSON response PreferHeader: type: string enum: - respond-async description: >- Controls synchronous vs asynchronous operation. See endpoint description above for behavior details. - `respond-async`: Makes request asynchronous, returns job status for polling - No value: Synchronous response FileUpload: description: >+ The file to process. It can be provided as a binary upload or as a JSON remote file reference. oneOf: - type: string format: binary description: |- #### Binary file Standard multipart file binary upload field - type: object title: Remote file properties: URL: type: string format: uri description: URL of the remote file to process contentType: type: string description: The MIME type of the remote file example: application/pdf required: - URL - contentType description: |- #### Remote file JSON objects containing file URL and content type, sent with specific multipart encoding: `type` and `filename`. The playground **doesn't support** them. Plase test with an alternative tool (Ex: Postman). Example cURL file field for remote file: ```bash --form 'file={ "URL":"https://your-file.pdf", "contentType":"application/pdf" } ;type=application/vnd.gonitro.url+json ;filename=https://your-file.pdf' ``` DeliverySingleFileOut: type: object properties: uploadResultTo: $ref: '#/components/schemas/HTTPCall' callback: $ref: '#/components/schemas/Callback' description: >- This endpoint lets you supply your own URL to receive the single-file output. The URL may point to a custom API endpoint or a pre-signed S3 URL. The HTTP method defaults to PUT, but you can change it based on your implementation needs via the `verb` parameter. You can also provide custom headers, such as authentication headers or any others required by your endpoint. PlatformOperationFileResult: type: object title: Sync - Single File properties: file: $ref: '#/components/schemas/FileInfo' AsyncJobResponse: type: object title: Async - Job properties: jobID: type: string example: 01234567-89ab-cdef-0123-456789abcdef status: type: string enum: - running progress: type: number description: Progress of the job as a float between 0.0 and 1.0 format: float default: 0 example: 0 HTTPCall: type: object properties: URL: type: string description: Your delivery endpoint URL nullable: false format: uri verb: type: string description: The HTTP method default: PUT enum: - GET - POST - PUT - DELETE - PATCH headers: type: array nullable: true description: Headers your file delivery endpoint might need (Optional) items: $ref: '#/components/schemas/Header' required: - URL - verb Callback: type: object description: >- POST endpoint that will get JOB ID and location when processing starts only on async processesing (see example above) properties: URL: type: string description: Your POST endpoint callback URL. nullable: false format: uri headers: type: array description: Headers your callback endpoint might need items: $ref: '#/components/schemas/Header' required: - URL FileInfo: type: object properties: URL: type: string format: uri description: >- URL with processed file for download. Field will be `null` if `delivery` parameter for post-processing upload is defined. nullable: true contentType: type: string description: The file type example: application/json metadata: type: object properties: fileSizeBytes: type: number nullable: true pageCount: type: number description: Number of pages in resulting document. nullable: true BadRequestProblemDetail: type: object description: Bad Request error details example: type: https://developers.gonitro.com/docs/build-nitro/errors#400-bad-request title: Bad Request status: 400 detail: Request validation failed instance: /platform/transformations allOf: - $ref: '#/components/schemas/ErrorResponse' UnauthorizedProblemDetail: type: object description: Unauthorized error details example: type: >- https://developers.gonitro.com/docs/build-nitro/errors#401-unauthorized title: Unauthorized status: 401 detail: Missing or invalid Authorization header instance: /platform/transformations allOf: - $ref: '#/components/schemas/ErrorResponse' NotFoundProblemDetail: type: object description: Not Found error details example: type: https://developers.gonitro.com/docs/build-nitro/errors#404-not-found title: Not Found status: 404 detail: Resource not found instance: /platform/transformations allOf: - $ref: '#/components/schemas/ErrorResponse' ContentTooLargeProblemDetail: type: object description: Content too large error details example: type: >- https://developers.gonitro.com/docs/build-nitro/errors#413-content-too-large title: Content too large status: 413 detail: Uploaded document exceeds the file size limit instance: /platform/transformations allOf: - $ref: '#/components/schemas/ErrorResponse' UnprocessableEntityProblemDetail: type: object description: Unprocessable Entity error details example: type: >- https://developers.gonitro.com/docs/build-nitro/errors#422-unprocessable-entity title: Unprocessable Entity status: 422 detail: The request was well-formed but could not be processed instance: /platform/transformations allOf: - $ref: '#/components/schemas/ErrorResponse' InternalServerErrorProblemDetail: type: object description: Internal Server Error details example: type: >- https://developers.gonitro.com/docs/build-nitro/errors#500-internal-server-error title: Internal Server Error status: 500 detail: An unexpected error occurred instance: /platform/transformations allOf: - $ref: '#/components/schemas/ErrorResponse' Header: type: object properties: name: type: string value: type: string required: - name - value ErrorResponse: type: object properties: type: type: string description: A URI reference that identifies the problem type title: type: string description: A short, human-readable summary of the problem type status: type: integer format: int32 description: The HTTP status code detail: type: string description: A human-readable explanation specific to this occurrence instance: type: string description: A URI reference that identifies the specific occurrence responses: BadRequest: description: Bad Request - Invalid request parameters content: application/problem+json: schema: $ref: '#/components/schemas/BadRequestProblemDetail' Unauthorized: description: Unauthorized - Invalid or missing Authorization header content: application/problem+json: schema: $ref: '#/components/schemas/UnauthorizedProblemDetail' NotFound: description: Not Found - Resource not found content: application/problem+json: schema: $ref: '#/components/schemas/NotFoundProblemDetail' ContentTooLarge: description: Content Too Large - File size exceeds limit content: application/problem+json: schema: $ref: '#/components/schemas/ContentTooLargeProblemDetail' UnprocessableEntity: description: Unprocessable Entity - Request cannot be processed content: application/problem+json: schema: $ref: '#/components/schemas/UnprocessableEntityProblemDetail' InternalServerError: description: Internal Server Error - An unexpected error occurred content: application/problem+json: schema: $ref: '#/components/schemas/InternalServerErrorProblemDetail' securitySchemes: BearerAuth: type: http scheme: bearer bearerFormat: JWT ````