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Playground demo key · api.reefapi.com
post/file-convert/v1/pdf_fill_form1 credit

AcroForm filling. Without 'fields' → lists the form fields (discovery). With 'fields' → fills and returns the PDF (NeedAppearances set). Output delivery: each produced file ≤10MB comes inline as base64 (files[].file_b64); 10-50MB comes as a one-time download token (files[].download_path, 30min TTL); >50MB total is rejected.

Working example
Parameters

The input file as base64 (data-URI prefix tolerated). Max 25MB. Provide file_b64 OR file_url. Multipart upload also works: POST the file as the 'file' form field.

https URL of the input file — fetched server-side through the proxy pool; private/internal/metadata addresses are SSRF-blocked. Max 25MB.

Optional original filename — used only as a hint (e.g. .md detection); the real format is always sniffed from magic bytes.

Password for encrypted PDFs. Without it an encrypted input fails cleanly with INVALID_PARAM (we never crack/bypass).

{field_name: value} map. Checkbox values are usually /Yes — run discovery mode first.

request preview
curl -X POST https://api.reefapi.com/file-convert/v1/pdf_fill_form \
  -H "x-api-key: $REEF_KEY" \
  -H "content-type: application/json" \
  -d '{"file_b64":"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"}'

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