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Fill PDF Form Fields API

What it does

PDF Form Filler fills an existing PDF form with field values and returns a completed PDF file. Send the form file, map text fields in values, set checkbox states in checked, and optionally set flatten to make the result non-editable.

Use it when you need to generate signed-up PDFs, onboarding packets, application forms, or internal paperwork from structured data. The input is a binary PDF form up to 20 MB. The field mappings are passed as JSON strings, so you can assemble them from your app data before upload.

The response is a binary PDF, ready to store, email, or hand off to the next step in your workflow. If you set flatten, the filled values are preserved in the document rather than left as editable form fields.

This is a fit for document automation pipelines where you already have the data and need a predictable way to render it into a PDF form.

POST
Fill a PDF form
https://api.eu.apyhub.com/freedailypro/fill-pdf-form-fields-api/form-fill

QUICKSTART

GUIDE

Quickstart

Fill a PDF form by uploading the PDF file.

curl -X POST "https://api.eu.apyhub.com/freedailypro/fill-pdf-form-fields-api/form-fill" \
  -H "apy-token: $APY_TOKEN" \
  -F "file=@/path/to/form.pdf"

What you'll get back

Returns the filled PDF as a binary file response.

TRY ITLIVE · 10 ATOMS
Loading your default key…
The full key is used to call the gateway and stays in this tab — never sent to orbit or saved.
Max 100MB total per request (all files combined). Larger? Use this API's URL-based endpoint instead, if it has one.
body*
The PDF form. Up to 20 MB.
JSON object of text field values, for example {"Name":"Ada"}
JSON object of checkbox states, for example {"Agree":true}
true to flatten the form so it can no longer be edited

About this endpoint

What it does

Uploads a PDF form and fills its fields with the provided values. The response is the resulting PDF file as binary data.

Request Body

ParameterTypeMandatoryDescription
fileStringYesThe PDF form. Up to 20 MB.
valuesStringNoJSON object of text field values, for example {"Name":"Ada"}.
checkedStringNoJSON object of checkbox states, for example {"Agree":true}.
flattenStringNotrue to flatten the form so it can no longer be edited.

Response

Returns a binary file containing the filled PDF form.

Max 100MB total per request (all files combined). Larger? Use this API's URL-based endpoint instead, if it has one.

▣ COMMON ERRORS

Errors any endpoint can return

400bad_request

Required parameter missing or malformed body.

401unauthorized

API key missing, revoked, or not authorized for this service.

429rate_limited

Your plan's per-second rate exceeded. Retry with exponential backoff.

503upstream_busy

Backend temporarily unavailable. Try again in a few seconds.

Similar APIs

Closest matches in the catalog based on this service.

CALLExtract PDF Form Fields APIFreeDailyProCALLTalk to PDF APIApyHubCALLCompress PDF File APIFreeDailyProCALLRotate PDF Pages APIFreeDailyPro

From the blog

Reads that touch this API.

HTML to PDF API: What It Does and Why Teams Use OneAug 19, 2026PDF Automation API Guide 2026: Generate, Merge, Watermark and Extract PDFsSep 22, 2026The Ultimate Guide to PDF Editing and Conversion Tools for Developers in 2025Jul 9, 2026Invoice Generator API: Create Invoice PDFs from JSON with PythonOct 25, 2026