A Docker service that automatically interleaves manually duplex-scanned PDFs.

When scanning documents on a scanner without auto-duplex, you scan all front pages first, then flip the stack and scan all back pages. The back pages come out in reverse order. Duplexer automatically interleaves these pages into the correct order.

Input: F1, F2, F3, ..., Fn, Bn, B(n-1), ..., B1 Output: F1, B1, F2, B2, F3, B3, ..., Fn, Bn

• Automatic interleaving of front and back pages
• Continuous directory watching with file stability checks
• Atomic writes - no partial files
• Idempotent - won't reprocess already-completed files
• Handles odd page counts (insert blank page or move to failed)
• Flexible file detection (stability-based or .ready sidecar files)
• Docker-ready with health checks

1. Drop your scanned PDFs in /ingest
2. Duplexer detects new files and waits for stability (default 5 seconds)
3. Pages are interleaved and written to /completed
4. Original is archived to /ingest/archive

Pull and run:

docker run -d \
  -v /path/to/scans:/ingest \
  -v /path/to/output:/completed \
  -e LOG_LEVEL=INFO \
  --name duplexer \
  ghcr.io/lipkau/duplexer:latest

Available tags:

• latest — Stable release (semver tags only)
• dev — Development build from main
• vX.X.X — Specific versions (e.g., v1.0.0)
• vX — Major versions (e.g., v1)

For Docker Compose examples (including paperless-ngx integration), see docker-compose.examples.md.

Duplexer uses hardcoded paths inside the container. Mount your directories via Docker:

docker run -d \
  -v /scans:/ingest \
  -v /output:/completed \
  -e LOG_LEVEL=DEBUG \
  -e FILE_STABILITY_SECONDS=10.0 \
  -e INSERT_BLANK_LASTBACK=true \
  -e OUTPUT_SUFFIX=.interleaved \
  --name duplexer \
  ghcr.io/lipkau/duplexer:latest

See docker-compose.examples.md for Docker Compose setup with paperless-ngx.