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Convert an HTML form to a fillable PDF in Ruby with Net::HTTP

A plain URL-to-PDF render gives you a picture of a form — nice to look at, impossible to type into. Setting "pdf_forms": true (with "format": "pdf") changes what comes back: every supported control on the page becomes a real AcroForm field at its exact rendered position, and the PDF can be filled in with Adobe Acrobat, macOS Preview, a browser viewer or a phone reader, then saved with the values kept.

Below is a complete, runnable Ruby program using Net::HTTP, no third-party dependency needed. It reads your API key from the SNAPDOK_KEY environment variable — free keys take about thirty seconds and need no card.

require "json"
require "net/http"
require "uri"

uri = URI("https://snapdok.io/v1/render")

res = Net::HTTP.start(uri.host, uri.port, use_ssl: true, read_timeout: 90) do |http|
  req = Net::HTTP::Post.new(uri)
  req["Authorization"] = "Bearer #{ENV.fetch("SNAPDOK_KEY")}"
  req["Content-Type"] = "application/json"
  req.body = JSON.generate({
    url: "https://your-app.com/intake-form",
    format: "pdf",
    pdf_forms: true,
})
  http.request(req)
end

raise "snapdok error #{res.code}: #{res.body}" unless res.is_a?(Net::HTTPSuccess)

File.binwrite("fillable.pdf", res.body)
puts "#{res["X-Form-Fields"]}  # AcroForm fields placed"

What converts: text-like <input>s (text, email, tel, date, password, number) become text fields — password renders masked and maxlength is enforced; <textarea> becomes a multiline field; checkboxes stay checkboxes; radio inputs sharing a name become a radio group with one choice across the group; <select> becomes a dropdown. Pre-filled values, readonly and checked state carry over.

What does not: file pickers, range sliders, color pickers, hidden or invisible inputs, forms inside iframes, and fake widgets built from styled divs. These are skipped cleanly and counted in X-Form-Skipped — never guessed at, never dropped in the wrong spot.

One layout consequence worth knowing before you file a bug: the forms path measures the page at paper width with print styles — the same geometry an ordinary PDF render uses — so the width parameter has no effect here, and a mobile-first page comes out in its paper layout, not its phone layout.

Notes for Net::HTTP

Stdlib only — no gems. The traps Net::HTTP is famous for, all handled in the sample: TLS is not automatic (set use_ssl: true or you will POST in the clear to port 80 and get a redirect); the default read_timeout of 60 s is close enough to real render times that raising it is wise; and the response body is a binary-ready String, but write it with File.binwrite — plain File.write on Windows would mangle line-ending bytes in the PDF. Check is_a?(Net::HTTPSuccess): Net::HTTP never raises on HTTP error statuses.

Response headers worth reading

Header	Meaning
`X-Form-Fields`	How many AcroForm fields were placed.
`X-Form-Skipped`	Controls skipped (unsupported or invisible).
`X-Cache`	HIT when served from the 24h cache — not charged.

Convert an HTML form to a fillable PDF in Ruby with Net::HTTP

Notes for Net::HTTP

Response headers worth reading

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