Case Study Productivity / Document Tools

PDFCatalyst — the PDF editor that never sees your files

Cloud PDF tools ask you to upload your tax documents and trust a deletion policy. We built one where every operation runs locally in the browser — your file never leaves the tab.

0files uploaded — zero outbound requests, verifiable in DevTools

15,000monthly active users within the first month

150 msaverage render time on a mid-tier laptop

10 weeksfrom concept to launch with a 4-person team

The Challenge

Privacy, friction, and broken Vietnamese text

Millions of professionals in Vietnam, ASEAN, and diaspora communities work with PDFs daily — and every existing tool forces an uncomfortable trade-off.

Privacy riskCloud editors store tax documents and contracts on external servers. "Deleted after 24 hours" is a promise, not a guarantee.

Cost & frictionDesktop suites cost $180–600 a year and demand installation — to fill a single form.

Corrupted diacriticsMost tools mangle Vietnamese text on export — "Nguyễn" comes out broken, making documents unusable for official filings.

The Solution

Privacy as architecture, not a checkbox

Every PDF operation — form filling, signatures, annotations, merge and split — runs locally via WebAssembly. There is no backend to breach because there is no backend at all.

01Open PDFpdf.js parses and renders in a Web Worker — the UI never blocks

02Edit locallypdf-lib in WebAssembly handles fills, signatures, and page ops in-browser

03AutosaveIndexedDB snapshots every 500ms; a session URL resumes work — no account needed

04Correct glyphsNon-ASCII text auto-loads a Vietnamese font family for pixel-correct diacritics

05Export cleanFont subset embedded, UTF-8 enforced — "Nguyễn" reads correctly in every viewer

No account requiredThe first prototype required email signup — 5% adoption. Session URLs replaced it and adoption hit 95%. Users bookmark and share links instead.

Vietnamese-firstCorrect diacritics drove ~40% of initial growth by word of mouth. Solving one thing extremely well beat solving everything averagely.

Nearly free to runA ~500KB static bundle on a global CDN costs about $50/month — versus $5K+/month for a comparable backend-driven product.

Technology

A stack with no servers to breach

RenderingMozilla pdf.jsIndustry-standard, battle-tested rendering engine

Editingpdf-lib (WebAssembly)Pure JS/WASM — no native binaries, no server round-trips

FrontendReact + TypeScriptType-safe, bilingual EN/VI from launch via react-i18next

StorageBrowser IndexedDBLocal-only sessions; AES-256-GCM encryption for saved profiles

HostingStatic CDN (Netlify)Sub-100ms first byte globally; no database, no auth service

QualityJest + Playwright + SentryVisual regression, Lighthouse CI, <0.5% JS error rate

Results

First month after launch

MetricMonth 1

Monthly active users~15,000

Documents edited~50,000

Export success rate99.1%

Return rate (bookmarked sessions)22%

Traffic from Vietnamese market~35%

Most-used features: form filling (65%), signatures (35%), annotations (28%). Security audit confirmed zero outbound file requests and no tracking fingerprints.

Two Products, Two Architectures

The right architecture for the problem

PDFCatalyst

Privacy-first productivity tool — everything runs in the browser

Zero backend: WebAssembly + static CDN, ~$50/month to run

4-person team, 10 weeks to launch

ClosIQ

B2B SaaS — real-time, multi-region

Heavy backend: Node.js, PostgreSQL, ML pipeline on AWS & Kubernetes

6-person team, 4 months to beta

Read the ClosIQ case study