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Use the PDF linearization API to optimize PDFs for web viewing. A linearized PDF is structured so viewers can start displaying the first pages before the entire file downloads, provided the file is served from a server that supports HTTP byte-range requests.

The /build endpoint handles PDF linearization. Add the source PDF as a parts item, set output.type to pdf, and set output.optimize.linearize to true.

For signup, pricing, and task-level examples, refer to the PDF linearization API task page.

Linearize a PDF

The following example linearizes document.pdf and writes the output to result.pdf:

curl -X POST https://api.nutrient.io/build \
-H "Authorization: Bearer your_api_key_here" \
-o result.pdf \
--fail \
-F document=@document.pdf \
-F instructions='{
"parts": [
{
"file": "document"
}
],
"output": {
"type": "pdf",
"optimize": {
"linearize": true
}
}
}'

Linearize 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:

{
"parts": [
{
"file": {
"url": "https://example.com/document.pdf"
}
}
],
"output": {
"type": "pdf",
"optimize": {
"linearize": true
}
}
}

Shell

Run this request to linearize a PDF from a URL:

Terminal window
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/document.pdf"
}
}
],
"output": {
"type": "pdf",
"optimize": {
"linearize": true
}
}
}' \
-o result.pdf

Linearize after assembling a PDF

Apply linearization to the final PDF that you plan to publish or deliver. You can assemble a document and linearize the assembled output in the same /build request.

The following example merges a cover page, body, and appendix, and then linearizes the final PDF:

{
"parts": [
{
"file": "cover"
},
{
"file": "body"
},
{
"file": "appendix"
}
],
"output": {
"type": "pdf",
"optimize": {
"linearize": true
}
}
}

Combine linearization with compression

You can combine linearization with other optimization options, such as mixed raster content (MRC) compression and image optimization.

Use this instructions object to combine linearization with compression:

{
"parts": [
{
"file": "document"
}
],
"output": {
"type": "pdf",
"optimize": {
"mrcCompression": true,
"imageOptimizationQuality": 2,
"linearize": true
}
}
}

For more compression options, refer to the PDF optimization API guide.

Linearize selected pages

Use parts[].pages to create a linearized output from only a selected page range. Page indexes are zero-based, and negative values count from the end of the document.

The following example extracts the first three pages and linearizes the resulting PDF:

{
"parts": [
{
"file": "document",
"pages": {
"start": 0,
"end": 2
}
}
],
"output": {
"type": "pdf",
"optimize": {
"linearize": true
}
}
}

The end value is inclusive, so { "start": 0, "end": 2 } includes pages zero, one, and two.

Linearize password-protected PDFs

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

{
"parts": [
{
"file": "protected_document",
"password": "document-password"
}
],
"output": {
"type": "pdf",
"optimize": {
"linearize": true
}
}
}

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

Publish linearized PDFs correctly

Linearization prepares the PDF for incremental loading, but delivery still depends on how you host the file. Follow these requirements when you publish the output:

  • Publish the linearized PDF from a server or object storage service that supports HTTP byte-range requests.
  • Use a PDF viewer that supports incremental loading.
  • Apply linearization to the final PDF after all content-changing operations are complete.

Use linearization before signing

Linearization changes the PDF file structure. If your workflow includes cryptographic signing, linearize the PDF before signing it. Treat signed PDFs as final artifacts.

A typical web delivery workflow includes these steps:

  1. Merge, split, rotate, fill forms, redact, or watermark the document.
  2. Optimize or linearize the final output.
  3. Apply a digital signature last, if required.
  4. Publish the signed output without further modification.

Reference

A PDF linearization request uses the Build API output.optimize.linearize option:

type OptimizePdf = {
// Linearize the output PDF for fast web viewing.
linearize?: boolean,
// Optional additional optimization settings.
mrcCompression?: boolean,
imageOptimizationQuality?: 1 | 2 | 3 | 4,
disableImages?: boolean,
grayscaleText?: boolean,
grayscaleGraphics?: boolean,
grayscaleImages?: boolean,
grayscaleFormFields?: boolean,
grayscaleAnnotations?: boolean,
};
type PDFOutput = {
type: "pdf",
optimize?: OptimizePdf,
};
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 include before linearization.
pages?: {
start?: number,
end?: number,
},
};
type BuildInstructions = {
parts: FilePart[],
output: PDFOutput,
};
  • Refer to the build document endpoint API reference to linearize PDFs and combine linearization with document assembly, page selection, compression, or security options.