SimplyFill vs DocSpring: which PDF-filling API fits your stack?
DocSpring is one of the longest-running products in the fill-a-PDF-via-API space, and if you're evaluating SimplyFill you've almost certainly got a DocSpring tab open too. Both products solve the same core problem: your application has the data, a PDF needs to be filled with it, and you'd rather make an API call than maintain a PDF library in-house.
The honest summary: DocSpring is a mature, editor-centric platform; SimplyFill is a newer, mapping-centric one. Which philosophy fits you depends on who on your team sets up templates and how often your forms change.
At a glance
| SimplyFill | DocSpring | |
|---|---|---|
| Field setup | AI reads visible labels and proposes semantic aliases, with confidence scores you review | Visual drag-and-drop template editor; automatic field detection from fillable PDFs |
| Field naming | Semantic aliases (fullName, invoiceNumber) decoupled from raw PDF names | Field names configured per template in the editor |
| HTML/CSS templates | No — fills existing PDFs | Yes — Liquid templating with logic, loops, and conditions |
| Multi-document output | Envelopes: one payload fans out into a packet of PDFs | One template per request |
| XFA forms | Auto-flattened to AcroForm on upload | Not prominently documented |
| Web forms | No hosted forms — you own the UI | Auto-generated web form per template, embeddable |
| E-signature fields | Sign-ready, flattened output for your e-sign tool | Signature field type supported in templates |
| API | REST, with Node.js and Python SDKs | REST |
| Compliance | SOC 2 Type II controls, HIPAA mode with BAA, US/EU/APAC regions | SOC 2 Type II, GDPR |
| Pricing model | Plan tiers — see pricing | $49/mo for 50 PDFs, $99/mo for 1,000, $249/mo for 5,000, plus per-PDF overage (as of June 2026) |
Where DocSpring is strong
It would be silly to pretend otherwise: DocSpring has been doing this for years and it shows.
- The template editor is genuinely good. If a non-developer on your team owns form setup, dragging fields onto a PDF in a visual editor is an approachable workflow.
- HTML/CSS templates with Liquid. If your documents are generated rather than filled — invoices or statements laid out from scratch — DocSpring lets you author them as HTML with loops and conditionals. SimplyFill deliberately doesn't do this; we fill existing PDFs.
- Hosted web forms. Every template gets an auto-generated web form you can embed. If you don't have an application UI collecting the data yet, that's a real shortcut.
- Maturity. Established product, established SLA on higher tiers, few surprises.
If those are the things you need most, DocSpring is a fine choice, and you should pick it without feeling like you're missing something.
Where SimplyFill is different
SimplyFill starts from a different observation: for teams that already have an
application, the expensive part of PDF automation isn't rendering — it's
mapping. Real-world PDFs name their fields f1_03[0] and Text12, and
someone has to figure out what those mean before any API can fill them.
- AI does the field archaeology. Upload a PDF and SimplyFill reads the visible labels and surrounding context — the same cues a human uses — and proposes a human-readable alias for every field, each with a confidence score and an evidence note ("nearby label 'DUE DATE'"). You review and publish instead of clicking through 40 fields by hand. We wrote up the mechanics in why PDF form fields have meaningless names.
- Mappings are a first-class object. The alias layer
(
fullName→topmostSubform[0].Page1[0].f1_07[0]) lives server-side and is versioned separately from your code. When a form is revised and its internal names shift, you re-map once; your application payload doesn't change. - Envelopes. One API call can fan a single payload out into a packet of filled PDFs — the pattern behind onboarding packets and application bundles — without orchestrating N requests yourself.
- XFA handling. Many government forms are XFA, which most PDF tooling chokes on. SimplyFill flattens XFA to standard AcroForm at upload time, so the fill call doesn't care what the source format was.
- Environments built in. Dev, staging, and production template versions with promotion between them, so a template edit can't silently change production output.
Pricing
DocSpring prices per PDF volume: as of June 2026, $49/month includes 50 PDFs, $99/month includes 1,000, and $249/month includes 5,000, with per-PDF overage rates after that ($0.25, $0.10, and $0.05 respectively). Unlimited test PDFs and templates on every tier — check their pricing page for current numbers.
SimplyFill's current plans are on the pricing section of this site. The shape to compare isn't just the sticker price — it's where your volume sits. At 50–100 PDFs a month almost anything is cheap; the divergence shows up when a workflow scales to thousands of documents and per-PDF overage starts to compound.
When to choose which
Choose DocSpring if:
- You're generating documents from scratch and want HTML/CSS + Liquid templates.
- A non-technical teammate owns template setup and wants a visual editor.
- You need hosted, embeddable web forms because there's no app UI yet.
Choose SimplyFill if:
- Your forms are existing PDFs — especially government or institutional ones with cryptic field names — and you want the mapping step automated.
- Your app already collects the data, and you want PDF output to be one clean API call with semantic field names.
- You need multi-document packets, XFA handling, or per-environment template versioning.
Try the difference on your ugliest form
The fastest way to compare is empirical: take the worst PDF in your workflow — the 40-field one with the field names nobody can read — and run it through both setup flows. The upload-to-mapped experience is where the two products differ most. Start with SimplyFill's quickstart; it takes about five minutes.