FillDef homeFillDef
AI-assisted · private by architecture

The PDF filler that
doesn’t upload your documents.

Fill any PDF for free, forever. Auto-fill from your encrypted profile, with AI matching the tricky fields: 5 trial fills your first 30 days, then 3 free per month.
$1.99 for 100 credits — no subscription, credits never expire.

Fill a PDF now — no signup.Get the Chrome extension

Try it without signing up — your file and values stay in this tab. Save them to a profile when you want auto-fill.

About the AI: when a field can’t be matched locally, only the field’s label is sent — never your data, never the document. Verifiable in your browser’s DevTools.
PDFs never leave your browser
AES-256-GCM encrypted profile
AI fallback for tricky fields
Built-in signature
No subscription · credits never expire
Verifiable in DevTools

How it works

1

Save your profile once

Name, address, tax IDs, signature — encrypted on your device. No account required to start.

2

Drop your PDF in

Fillable W-9, NDA, lease, government form — a local dictionary auto-fills 80–90% of fields instantly, and an AI fallback handles the tricky ones (label-only, never your data). Nothing uploads.

3

Review, sign, download

Edit any value, click to drop your signature anywhere, download. One credit covers the upload and every re-download.

The PDF tweak surface

Fill it. Fix it. Sign it.
Without spending another credit.

Other PDF fillers commit on click. Wrong field? Re-upload. Misplaced signature? Re-upload — and pay again. FillDef opens every fill in a review surface so you can correct typos, drop saved values onto blank space, and place your signature exactly where it belongs. One credit covers the upload and every re-download.

Works with fillable PDFs (W-9, government forms, most insurance and HR docs) and non-fillable PDFs — scanned leases, exported flat PDFs, anything without form widgets. We detect the file type on upload and switch to manual placement mode before any credit is spent.

✎ signature
form-w9.pdf
Ready·112 KB
Edit, pick, and remove unlimitedFree fill
Typography
Paid
Helvetica
11pt
Unlocks on any paid fill → font + size 8–24pt
Fields
Full name
John Doe
Date of birth
1990-01-15
Tax ID
edited
12-3456789
Address
1 Market St, San Francisco

Edit before you commit

Every value the dictionary or AI auto-fills is editable in place. Wrong middle name? One click. Tweaks are unlimited on every fill — free, trial, or paid.

Drop any value, anywhere

Pick from your profile (or type free text), then click to drop it on the page. Works on fillable PDFs as a tweak, and on non-fillable PDFs as the primary fill mode — no form widgets required.

Click-to-place signature

Save your signature once. Click anywhere on the PDF to drop it. Free fills lock the placement; paid fills make it draggable and resizable.

Restyle the whole document

Paid fills unlock font family and size (8–24pt). Standard fonts only — no font-bundle bloat.

Try the PDF filler
Privacy by architecture

Privacy isn’t a policy. It’s how we built it.

PDFs never leave the browser

Upload, map, fill, sign, download — all inside your browser. The file bytes never reach a server.

Profile encrypted before it leaves your device

AES-256-GCM encryption with a key derived from your account. Our servers store only ciphertext they can't read — your name, address, and tax ID are never visible to us. The key never leaves your browser.

AI sees labels, not values

When the local dictionary misses, only the field label — for example, "Steueridentifikationsnummer" — is sent. Never your tax ID, never the document.

Read the full privacy story →

How FillDef compares

Smallpdf and Adobe upload your file. SimplePDF keeps it local but makes you type every field. FillDef does both — local, and auto-filled from your saved profile.

FillDefSimplePDFSmallpdfAdobe Acrobat
PDF stays in your browser (no upload)
Auto-fills from a saved profile
partial
Multi-profile (juggle clients)
Built-in signature, click-to-place
partial
Free tier without watermark
partial
No subscription required
Bonus: web-form autofill (Chrome)

Comparison reflects each tool’s default free or entry tier as of May 2026. Web-form autofill requires the FillDef Chrome extension.

And also: web formsOptional Chrome extension

Same encrypted profile, also fills web forms.

Install the Chrome extension when you’re ready — or skip it entirely. Web forms autofill from the same profile your PDFs use. A local pattern dictionary handles 80–90% of fields instantly; the AI fallback only sees field labels, never your data.

  • Pattern matches in milliseconds, fully offline.
  • Inline override badges to swap a saved value into any field.
  • Same credit pack covers PDF fills and web fills.
Get the extensionChrome only for now · Firefox & Edge on the roadmap
application.gov/form
FillDef
Full name
John Doe
Email
[email protected]
Phone
+1 555 010 1234
Address
1 Market St, San Francisco
4 fields filled · 0 values sent to a server

Pay once. Fill forever.

No subscription. Credits never expire. 3 fills are free every month (plus 5 trial fills your first 30 days) — buy a pack only when you outgrow it. Power pack is $0.013 per fill, less than two cents.

See pricing

Questions, answered.

Do I need to sign up?
No. You can upload a PDF, place values and your signature, and download — entirely in your browser, no account, no email. Sign up only when you want to keep what you typed: a saved encrypted profile auto-fills every recognized field on the next PDF, saves your signature, and gives you 3 free auto-fills every month from day one — plus 5 paid-level trial fills layered on top during your first 30 days. Without signup, the values you place live in this browser tab only — close it and they're gone, which is also how we make sure we never have anything to leak.
How is this different from SimplePDF?
SimplePDF is the closest thing out there — same browser-local philosophy, no upload, no watermark. Where FillDef goes further: every field auto-fills from your saved encrypted profile (SimplePDF makes you type each time), you can keep multiple profiles for different clients, and the signature places with one click without leaving the page. If SimplePDF is a good PDF editor that respects your privacy, FillDef is a PDF filler — autofill is the whole point.
What does the AI actually see?
Field labels only. When the local dictionary can't match a field (about 10–20% of fields, mostly non-English or unusual labels), FillDef sends only the label text — e.g. "Steueridentifikationsnummer" — to Gemini Flash-Lite. The PDF bytes, your profile values, and any of your typed text never leave the browser. You can verify it yourself in DevTools → Network: one POST to /fields-map per fill, with labels in the body and nothing else.
Do I need to install anything?
No. The web app fills PDFs entirely in your browser — open it, drop a PDF, download. No signup needed to start the demo. The Chrome extension is optional and only adds web-form autofill on top.
Do you store the PDFs I fill?
No. PDFs are read, filled, and downloaded entirely inside your browser. The bytes never reach our servers — you can confirm in DevTools that no upload request happens.
What kind of PDFs work?
Both fillable and non-fillable PDFs. Fillable PDFs (W-9, most government forms, insurance and HR documents) get auto-mapped to your profile. Non-fillable PDFs — scanned leases, flat exports, anything without form widgets — drop you into manual placement mode where you click to drop saved values anywhere on the page. FillDef detects the file type on upload and tells you what to expect before any credit is spent.
How do free vs paid PDF fills work?
Before each PDF is mapped, FillDef shows a Choose-credit screen with your trial fills (5, first 30 days), free-fill quota (3/month), and your paid balance side by side. Every fill type unlocks unlimited tweaks and unlimited fixed-size signature placement; paid and trial fills additionally unlock font controls and a draggable, resizable signature. You decide every time. There's also a manual fill mode — no autofill, never costs anything.
Why credits instead of a subscription?
You shouldn't pay every month for a tool you use twice a quarter. Buy 100 credits for $2.99 and use them whenever — they don't expire. Three fills are free every month, no card required — plus 5 trial fills your first 30 days. No auto-renewal, no "downgrade to free" dark patterns.
Can I also autofill web forms?
Yes — the FillDef Chrome extension uses the same encrypted profile to autofill web forms (job applications, signups, vendor onboarding). It's optional. Chrome only for now; Firefox and Edge are on the roadmap. Your login and credit balance are shared between the web app and the extension.
What happens if I uninstall the extension?
Nothing — your encrypted profile lives on our servers (we can't decrypt it) and isn't affected. The extension keeps its own local cache for offline form-filling, and the browser deletes that cache on uninstall, but the canonical copy stays intact on the server. Reinstall later and it re-syncs automatically.
What does AI cost me?
Nothing extra. AI fallback only runs on field labels the local dictionary can't match (~10–20% of fields). One fill costs one credit, whether it's pure dictionary, pure AI, or a mix.

Three fills a month, no card required.

No trial countdown. No “downgrade to free” dark patterns. Buy credits only if you outgrow the free tier — and they never expire.

Try the PDF fillerHow we keep your data private