PDF to PDF/A - Nitro APIs

POST

conversions

PDF to PDF/A

curl --request POST \
  --url https://api.gonitro.dev/conversions \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form method=convert \
  --form 'params={
  "to": "pdfa",
  "conformance": "2b",
  "imageQuality": 0.8,
  "copyMetadata": true
}' \
  --form 'file=<string>' \
  --form file.0='@example-file'

{
  "file": {
    "URL": "<string>",
    "contentType": "application/json",
    "metadata": {
      "fileSizeBytes": 123,
      "pageCount": 123
    }
  }
}

The PDF to PDF/A feature of the Conversions endpoint converts a standard PDF into a PDF/A archival format. PDF/A is an ISO-standardized subset of PDF designed for long-term preservation — it embeds all fonts, colour profiles, and metadata required to render the document identically in the future without any external dependencies.

Conformance levels

PDF/A comes in three generations (1, 2, 3) and three conformance tiers (b, u, a):

Level	Name	Description
`1b`	PDF/A-1b	Basic visual-appearance conformance. No special document structure required.
`1a`	PDF/A-1a	Accessible conformance. Requires a tagged PDF (logical document structure).
`2b`	PDF/A-2b	Basic conformance for PDF 1.7 features: JPEG2000 images, transparency, and layers.
`2u`	PDF/A-2u	Unicode conformance. Like `2b`, plus guarantees all text is Unicode-mappable for reliable search and copy.
`2a`	PDF/A-2a	Accessible conformance for PDF 1.7 features. Requires a tagged PDF.
`3b`	PDF/A-3b	Like `2b`, but also permits embedding arbitrary files (e.g. XML, CSV) inside the PDF.
`3u`	PDF/A-3u	Unicode conformance for PDF/A-3 feature set.
`3a`	PDF/A-3a	Accessible conformance for PDF/A-3. Requires a tagged PDF.

Conformance levels ending in a (accessible) require the source PDF to be tagged — that is, it must contain a logical structure tree. Submitting an untagged PDF to an a-level conformance target will return an error. Use b or u variants for general-purpose archiving.

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 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 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:
```
    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 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:
```
{
    "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 100 MB per request. This applies to single-file and multi-file requests.
Page count: Maximum of 500 pages per individual document. This applies to single-file and multi-file requests. Multiple documents may exceed 500 pages in total.
Retention time: Inputs and outputs are deleted approximately 15 minutes after the operation completes.

Request

Authorizations

Authorization

string

header

required

Bearer authentication header of the form Bearer <token>, where <token> is your auth token.

Headers

enum<string>

default:*/*

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

Available options:

application/json,

application/octet-stream,

*/*

Prefer

enum<string>

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

Available options:

respond-async

Body

multipart/form-data

method

enum<string>

default:convert

required

The Conversions' endpoint method: convert

Available options:

convert

params

PDF/A · object

required

Show child attributes

file

required

The file to process. It can be provided as a binary upload or as a JSON remote file reference.

delivery

object

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.

Show child attributes

Response

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.

Sync - Single File
Async - Job

file

object

Show child attributes

Job StatusGet status of asynchronous Job. A Job is Nitro’s asynchronous file processing for PDF Transformation, Conversion, and Extraction operations.

PDF to PDF/A

curl --request POST \
  --url https://api.gonitro.dev/conversions \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form method=convert \
  --form 'params={
  "to": "pdfa",
  "conformance": "2b",
  "imageQuality": 0.8,
  "copyMetadata": true
}' \
  --form 'file=<string>' \
  --form file.0='@example-file'

{
  "file": {
    "URL": "<string>",
    "contentType": "application/json",
    "metadata": {
      "fileSizeBytes": 123,
      "pageCount": 123
    }
  }
}

​Conformance levels

​Output File Format

​Processing

​Custom File Delivery

​Sync delivery

​Custom endpoint

​S3 delivery

​Async delivery

​Callback

​Response behavior Matrix

​Limits

​Request

Authorizations

Headers

Body

Response

Conformance levels

Output File Format

Processing

Custom File Delivery

Sync delivery

Custom endpoint

S3 delivery

Async delivery

Callback

Response behavior Matrix

Limits

Request