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Edit fills PDF forms and modifies DOCX documents using natural language instructions. You describe what values should go where, and Edit handles field detection, mapping, and insertion. While Parse reads documents and Extract pulls specific data out, Edit writes data back in. This completes the document processing loop: parse a document to understand it, extract data from one source, edit that data into a different form.
The Edit endpoint is available in the Python SDK, Node.js SDK, and via cURL. The Go SDK does not yet support Edit.

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When to Use Edit

Edit solves form filling at scale. Instead of manually clicking through fillable PDFs or templating Word documents, you describe what you want in natural language. Common use cases:
  • Filling government and tax forms (W-9, I-9, G-1145) with applicant data
  • Completing insurance applications and claim forms
  • Populating legal contracts with client information
  • Generating customized DOCX reports from extracted data
PDF libraries like PyPDF require knowing exact field names and coordinates. Edit uses AI to understand field context, so “Fill in the applicant name” works even if the PDF field is named topmostSubform[0].Page1[0].f1_1[0].

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Quick Start

from pathlib import Path
from reducto import Reducto

client = Reducto()
upload = client.upload(file=Path("w9_form.pdf"))

result = client.edit.run(
    document_url=upload.file_id,
    edit_instructions="""
        Fill this W-9 form with:
        - Name: Acme Corporation
        - Business name: Acme Corp LLC
        - Tax classification: LLC
        - Address: 123 Main Street, San Francisco, CA 94102
        - TIN: 12-3456789
    """
)

print(result.document_url)  # Download the filled form
What happens:
  1. Edit detects all fillable fields in the PDF (text boxes, checkboxes, dropdowns)
  2. An LLM reads your instructions and field context (labels, surrounding text)
  3. Each field gets mapped to the appropriate value
  4. The filled PDF is returned as a downloadable URL

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PDF vs DOCX

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PDF

PDFs have structured form widgets (text fields, checkboxes, dropdowns). For PDFs without existing form fields, Edit uses vision to detect where fillable areas should be.
FeatureDescription
Text fieldsFill any text input area
CheckboxesCheck or uncheck based on instructions
DropdownsChoose from available options
Form detectionFinds fields even in scanned forms
OverflowLong text can flow to appendix pages

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DOCX

DOCX supports richer editing because the format allows inline content modification.
FeatureDescription
Form fieldsModern (2007+) and legacy form controls
CheckboxesBoth modern and legacy controls
Table cellsModify or append to existing cell content
Text insertionInsert content at paragraph markers
HighlightingEdits get highlighted in configurable color

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Request Parameters

result = client.edit.run(
    document_url="...",           # Required: file to edit
    edit_instructions="...",      # Required: what to fill
    edit_options={
        "color": "#FF0000",                  # Highlight color (DOCX only)
        "enable_overflow_pages": False,      # Appendix for long text (PDF only)
        "llm_provider_preference": "openai"  # LLM provider (optional)
    },
    form_schema=[...]             # Optional: predefined field locations (PDF only)
)

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document_url

The document to edit. Accepts the same formats as Parse: reducto:// file IDs from upload, public URLs, or presigned S3/GCS URLs.

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edit_instructions

Natural language instructions describing what to fill. Be explicit about values and which fields they belong to: 
Fill this form with:
- Full Name: John David Smith
- Date of Birth: March 15, 1985
- SSN: 123-45-6789
- Check "Yes" for US Citizen
- Select "California" for state
Vague instructions like “Fill out John’s information” perform poorly. Include formatting hints when the form expects specific formats (dates, phone numbers, SSNs).

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edit_options

OptionDefaultDescription
color#FF0000Hex color for highlighting edits (DOCX only)
enable_overflow_pagesfalseCreate appendix pages for text exceeding field capacity (PDF only)
llm_provider_preferencenullLLM provider for form filling: "openai", "anthropic", or "google". If null, defaults to Google.

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form_schema

For repeatable form filling, define field locations explicitly. This skips detection, improving speed 3x and consistency. See Form Schema.

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Response

{
  "document_url": "https://storage.reducto.ai/filled-form.pdf?...",
  "form_schema": [
    {
      "bbox": {"left": 0.1, "top": 0.2, "width": 0.4, "height": 0.03, "page": 1},
      "description": "Name field in header section",
      "type": "text"
    }
  ],
  "usage": {"num_pages": 2, "credits": 8}
}
FieldDescription
document_urlPresigned URL to download edited document. Valid 24 hours.
form_schemaDetected field schema (PDF only). Save this to reuse for the same form type.
usage.creditsCredits charged: 4 per page.

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Async Processing

For larger documents or webhook delivery, use the async endpoint: 
result = client.edit.run_job(
    document_url=upload.file_id,
    edit_instructions="...",
)
print(result.job_id)  # Poll /job/{job_id} or wait for webhook

# Poll for results
import time
while True:
    job = client.job.get(result.job_id)
    if job.status == "Completed":
        print(job.result.document_url)
        break
    time.sleep(2)
Sync requests get priority by default. Async can request priority with priority=True if your account has budget available.

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How It Works

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PDF

  1. Detect form widgets (or use vision if none exist)
  2. Analyze context around each field (labels, headers)
  3. Map your instructions to fields based on descriptions
  4. Fill values into the PDF
With a form_schema, steps 1-2 are skipped since you’ve defined field locations and descriptions.

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DOCX

  1. Tag editable locations (paragraphs, table cells, form controls)
  2. Analyze document structure against your instructions
  3. Generate specific edits (insert text, check boxes, update cells)
  4. Apply edits with optional highlighting

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Troubleshooting

Several things can cause unfilled fields:
  • Instructions didn’t match: The LLM couldn’t map your instructions to that field. Use terms that appear on the form itself.
  • Dropdown mismatch: Value must exactly match an option (“CA” vs “California”)
  • Detection missed it: Use form_schema to explicitly define field locations
The PDF has no widgets and vision couldn’t detect fillable areas. Common causes:
  • Scanned image without clear form structure
  • Fields blend into background or lack clear boundaries
  • Document isn’t actually a fillable form
Solution: Provide a form_schema defining field locations. See Form Schema.
PDF fields have fixed sizes. When content exceeds capacity, it gets truncated.Solutions:
  1. Enable overflow: edit_options={"enable_overflow_pages": True} creates appendix pages
  2. Abbreviate in your instructions if the form expects short values
Be explicit: Check "Yes" for US Citizen works better than US Citizen: Yes. The LLM needs to understand you mean check a box, not fill text.
When fields have similar labels, the LLM may map incorrectly:
  1. Be more specific: “Applicant First Name: John” rather than “Name: John”
  2. Use form_schema: Define exactly which field is which using coordinates
  3. Reference position: “The name field in the top-left of page 1”
No. Parse finds existing content (labels like “Name:”). Edit finds empty fillable areas (the input box next to “Name:”). Form fields are blank rectangles with nothing for Parse to detect.Use Edit once without form_schema to detect fields, then save and reuse the returned schema.

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Limitations

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Partial Success

Edit returns successfully even when some fields couldn’t be filled. These situations don’t raise errors:
ScenarioBehavior
Dropdown value not in optionsField skipped silently
Instructions don’t match any fieldDocument returned unchanged
Unsupported widget (signatures, images)Widget skipped

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Format-Specific

PDF:
  • Signature and image fields not supported
  • Radio buttons have limited support
  • Heavily designed forms may detect incorrectly
DOCX:
  • Requires structured documents (form controls, tables)
  • Very large documents (100+ pages) take longer

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Next Steps

Form Schema

Pre-define field locations for faster, more consistent filling.

API Reference

Complete endpoint specification.