Every tool in this list can get a PDF form completed. The difference is how much of the work it does for you — and that matters, because form filling is pure admin, and small business owners already spend around 16 hours a week (roughly a third of the workweek) on administrative tasks like data entry and invoicing.
The best tool depends on the job: Filly AI is best for filling forms repeatedly — it auto-detects fields with AI (OCR for scans), fills them from saved client profiles, and batch-fills for many clients at once. Adobe Acrobat is best for editing PDFs. DocuSign is best for signature-heavy approval workflows. Smallpdf is best for quick one-off conversions and edits. Filling by hand is free but doesn't scale past a handful of forms.
The five options at a glance
| Tool | Best for | Auto-fill from saved data | Handles scanned forms | E-signature | Free tier |
|---|---|---|---|---|---|
| Filly AI | Filling many forms fast (clients, intake, government forms) | Yes — AI + reusable profiles, batch fill | Yes (OCR) | No-login link | 10 fills/month |
| Adobe Acrobat | Editing PDFs; occasional manual fill | No | Partially (makes scans fillable, you still type) | Acrobat Sign | Limited web tools |
| DocuSign | Signature and approval workflows | Template fields, no AI fill | No | Yes — core product | Trial only |
| Smallpdf | Quick one-off edits and conversions | No | No | Basic | Limited daily use |
| By hand (print or type) | A single short form, once | No | — | Wet ink | Free |
When does an AI form filler actually pay off?
The break-even is repetition. If you complete one form a month, any free editor is fine. If you complete the same forms for different people — a law practice preparing government forms, an agency onboarding clients, a landlord processing applications — the retyping is the cost. An AI filler reads the form once and reuses stored details, so the tenth form takes seconds, not minutes. That's the difference between a filler and an editor: editors make typing possible; fillers make it unnecessary.
What about getting the form signed?
Signature is where online tools beat paper decisively. Industry studies report about 79% of e-signed agreements complete within 24 hours — around half within 15 minutes — and e-sign transactions show far higher completion rates than paper-based equivalents. DocuSign is the standard for multi-step approval chains; for the simpler case of "fill this and get one signature back," Filly's no-login link (the recipient signs in the browser, no account) covers it without a separate subscription.
How should you choose?
- You mostly edit documents: Adobe Acrobat.
- You mostly route documents for signature: DocuSign.
- You occasionally tweak or convert a PDF: Smallpdf.
- You fill forms for clients, repeatedly: Filly AI — start with the free plan and test it on your worst form. See how it compares with Acrobat in detail, including whether Adobe Fill & Sign uses AI.
Frequently asked questions
Can any of these fill a scanned, non-fillable PDF automatically?
Filly AI reads scans with OCR and places values onto the page automatically. Acrobat can convert a scan into a fillable form, but you still type the answers yourself. Whichever you use, the scan itself usually needs tidying first — a phone photo comes in sideways and a desk scanner returns twenty pages as one file. Rotating sideways pages and splitting a scanned batch back into separate documents are the two that come up every time.
What does "batch fill" mean?
One form, many people: pick a form and a set of saved client profiles, and get one completed document per client in a single run — useful for intake packets, renewals, and notices.
Are there free options?
Yes. Filly's free plan includes 10 fills a month with no credit card, and Smallpdf allows limited free daily use. Acrobat's free web tools cover viewing and basic filling. See Filly pricing for the paid tiers.
Can any of these pull the data straight from my CRM, ATS or HR system?
Partly, and the distinction matters more than the marketing suggests: filling the fields of a PDF you already have is a different product from generating a new document that merely looks similar. If the layout is a W-4, an I-9 or a lender's own template, only the first is any use. The CRM, ATS and HR comparison works through which tools do which, and why Zapier and Make move the data but do not fill PDF fields with their own native steps.
Is there an API for this?
Some of these have one and some do not — Filly does not, which rules it out if you need a filled PDF produced the moment a record changes. For that case a library or a hosted filling API is the right answer, and the real cost is never the code but the field map somebody has to maintain when an agency reissues the form. The developer comparison covers pdf-lib, PDFtk and the API options honestly, including when a library beats paying per fill.
Which is best for legal or government forms?
Forms that arrive as flat or scanned PDFs (common with government agencies) need OCR plus accurate field placement — that's Filly's core use case. There are also ready-made templates for common contracts and legal documents. USCIS immigration filings are their own category, because most of the tools recommended for them are not form fillers at all — the immigration comparison sorts the practice-management suites, done-for-you services and case trackers from the tools that actually put text into the PDF.