New API-first proofing for print and prepress

Proof customer PDFs without breaking production.

PDFModule Proofing turns preflight data, PDF previews, comments, approvals, versions, and audit trail into one print-native workflow. Simple enough for a customer on mobile. Reliable enough for prepress.

Open Proofing App Review API model
Customer-first review Open from email, comment, approve or reject in seconds.
Print-native core Trim, bleed, safe zone, page-level issues and later full preflight overlays.
Sellable architecture SaaS, embedded viewer, API integration and white-label tenant model from the start.
3 Bleed missing on page 2
Customer Move price block 4 mm up.
Prepress Spot color not mapped yet.
Status Approve with comments
1 link Guest-safe proof access with expiry and PIN.
1 source Version history, approvals and comments stay attached to the job.
1 API Create proofs, upload versions, sync status, receive webhooks.

Built for print teams, not generic document review.

The product line should solve the real handoff between customer, project manager, artwork, prepress and production. That means zero email chaos outside the system and no ambiguity about which version was approved.

What breaks in the usual flow

Most proof cycles fail because approval is easy to ask for but hard to trust.

  • Feedback gets buried in email threads and screenshots.
  • Customers approve the wrong version or approve with unresolved issues.
  • Production systems have no reliable event model to sync against.
  • Generic review tools stop at markup and ignore prepress context.

What PDFModule Proofing should do

The proof should feel lightweight to the customer and strict to the factory.

  • One secure link opens a responsive viewer on desktop, tablet or phone.
  • Comments, approvals, versions and audit events all attach to one proof record.
  • Every meaningful state change is available through API and webhook events.
  • Preflight issues become first-class proof data instead of a separate silo.

The workflow stays simple on the outside.

MVP should optimize for a customer opening a link on mobile and approving in under 30 seconds, while the internals keep enough structure for production-grade traceability.

1

Create proof

Production system or user creates a proof container with job reference, participants and status.

2

Upload version

PDF lands once, rendering jobs fan out, thumbnails appear progressively and current version updates.

3

Review and comment

Customers and internal users annotate with stable document coordinates, reply in threads and resolve issues.

4

Approve or reject

Decision attaches to a specific version, logs open comment state, and syncs back via webhook/API.

Core product bet

The differentiator is not "comments on a PDF". It is combining proof review with the same PDF intelligence that already powers PDFModule preflight and correction workflows.

Recommended system architecture

Start as a modular monolith in TypeScript, keep storage and jobs externalized, and split services later only if load or team boundaries justify it. This keeps the MVP shippable without building microservice theatre.

Proof Service

Owns proof container, versions, participants, lifecycle state and approval decisions.

Proof Versioning Status model

Asset Pipeline

Stores source PDFs, page renders, thumbnails and signed URLs for embedded or public viewer sessions.

S3-compatible storage CDN Async rendering

Annotation Service

Stores point, box and page comments with thread status, visibility and normalized page coordinates.

Threads Internal vs external Stable coordinates

Workflow + Notification

Handles invitations, reminders, mail events, webhook delivery and retry-safe outbound messaging.

Mail Reminders Webhooks

Auth + Access

Combines tenant users, guest sessions, expiring proof links, scoped tokens and optional PIN protection.

Tenant isolation Guest reviewer Scoped access

Preflight Integration Layer

Maps PDFModule preflight results to pages and later overlays, without coupling proof UX to one engine implementation.

Issue mapping Severity Production sync

Viewer and annotation model

The viewer is the product. If zoom, touch and coordinates drift, the platform becomes expensive noise. MVP should therefore prioritize deterministic page rendering and a strict coordinate system over fancy annotation tools.

Rendering strategy

Pre-render preview assets per page in the background. Stream thumbnails first, then standard preview, then higher zoom levels as needed.

Progressive load Large PDF safety

Coordinate system

Store x, y, width and height as normalized page coordinates relative to PDF page space, never viewport pixels.

Zoom-safe Device-safe

Responsive rules

Mobile gets page browsing, zoom, comments and approval. Desktop adds compare, overlays and dense comment management.

Mobile-first Desktop-power
Pragmatic compare for MVP+

Do not start with full visual diff. Start with side-by-side version compare and changed-page detection based on rendered page hash or PDF object/page fingerprinting. Layer in visual diff later if it proves reliable enough.

Concrete data model

The schema should reflect product truth directly: proofs contain versions, versions contain pages and preflight issues, and approvals always point to the exact version that was accepted or rejected.

Tenant

Plan, branding, API credentials, webhook config and usage limits for SaaS and white-label isolation.

plan branding_settings api_credentials

Proof

Root business object with external reference, title, status, current version, created by and participant summary.

external_reference current_version_id status

ProofVersion + ProofPage

Version metadata, render status, file source and page-level assets, dimensions and page counts.

version_number render_status preview_asset_url

Comment

Threaded annotations with author identity, visibility, status and normalized coordinate payload per page.

bbox visibility resolved_at

ApprovalDecision + GuestAccess

Version-bound decisions, reviewer identity, link tokens, expiry, PIN hash and scope rules for external access.

decision token_expires_at pin_hash

AuditEvent + PreflightIssue

Immutable event log plus issue records mapped to page and region when coordinates exist.

event_type payload severity

High-level API contract

REST is enough for MVP if it is consistent, idempotent on critical writes, and backed by signed webhook delivery. Realtime comments can use SSE or WebSocket later without changing the resource model.

Core resources

POST   /api/v1/proofs
GET    /api/v1/proofs/{id}
PATCH  /api/v1/proofs/{id}
POST   /api/v1/proofs/{id}/versions
GET    /api/v1/proofs/{id}/versions
GET    /api/v1/proofs/{id}/pages
POST   /api/v1/proofs/{id}/comments
GET    /api/v1/proofs/{id}/comments
PATCH  /api/v1/comments/{id}
POST   /api/v1/proofs/{id}/approve
POST   /api/v1/proofs/{id}/reject
POST   /api/v1/proofs/{id}/invite
GET    /api/v1/proofs/{id}/audit
GET    /api/v1/proofs/{id}/preflight-issues

Critical POST calls should support idempotency keys, especially proof creation, version upload and approval endpoints.

Webhook events

{
  "event_id": "evt_01J...",
  "type": "proof.approved",
  "occurred_at": "2026-03-21T09:12:33Z",
  "tenant_id": "ten_123",
  "proof_id": "prf_456",
  "version_id": "ver_9",
  "signature": "v1=...",
  "data": {
    "decision": "approved_with_comments",
    "open_comment_count": 1,
    "external_reference": "JOB-20483"
  }
}

Ship with retry strategy, HMAC signing, dead-letter handling and event replay tooling for support.

Phased MVP roadmap

Keep phase 1 tight enough to launch, phase 2 focused on workflow lift, and phase 3 reserved for the features that truly separate PDFModule from generic approval tools.

Phase 1

Must-have foundation

Proof object, PDF versioning, thumbnails and previews, point/box comments, approvals, guest link access, notifications, audit trail and API/webhooks.

Launchable Customer usable Production sync
Phase 2

Workflow depth

Comment filters, internal vs external discussion, reminders, deadlines, multiple approvers, changed-page detection and side-by-side compare.

Operational lift Revision handling
Phase 3

Category differentiators

Preflight overlays, trim/bleed/safe-zone visualization, issue-to-proof mapping, deeper production integration and white-label embedded viewer packages.

Print-native moat SaaS expansion

Recommended tech stack

Use a stack that is easy to hire for, straightforward to operate, and naturally compatible with PDFModule's existing API orientation.

Frontend

Next.js or React SPA with a purpose-built viewer shell, touch-friendly comment UX and progressive asset loading.

React Responsive UI Embeddable viewer

Backend

Node.js + TypeScript modular monolith with clear domains for proofs, assets, comments, auth, workflow and webhooks.

TypeScript Fast iteration Split later if needed

Data + jobs

PostgreSQL for relational truth, Redis-backed queue for rendering and notifications, S3-compatible object storage plus CDN.

PostgreSQL Queue workers CDN-backed assets
Deployment model

Run the API and workers separately, keep rendering and compare jobs asynchronous, and make signed asset delivery CDN-friendly from day one. That gives you SaaS scale without forcing distributed-system complexity into the first release.

Technical risks that matter

These are the areas that can quietly destroy trust if they are handled casually. They should drive architecture and QA from the beginning.

PDF rendering and scale

Large files, many pages and high zoom levels will kill UX unless previews are progressive and rendering is isolated in background jobs.

Annotation precision

Coordinates tied to viewport pixels will drift across zoom levels and devices. Normalized document coordinates are non-negotiable.

Mobile review friction

If comment entry and approval feel awkward on phones, customers will bounce back to email immediately.

Compare expectations

Promising full visual diff too early is a trap. Changed-page detection is safer and ships faster.

Guest access security

Token leakage, long-lived links and no rate limiting will turn proof links into a liability. Use expiry, scope and optional PIN.

Multi-tenant isolation

White-label and SaaS only work if proof access, assets, webhooks and API keys are tenant-scoped all the way down.

PDFModule Proofing extends the platform from PDF output to production-ready approval.

The practical MVP is clear: ship the viewer, version history, annotations, approvals, audit log and integration hooks first. Then layer in compare and deep preflight overlays as the differentiating second wave.

Open Proofing App See Preflight Positioning