Automating Document Conversion at Scale: Scripts and Tools to Replace M365 in CI/CD

Stop paying for document conversion in your CI/CD: practical scripts and patterns using LibreOffice headless

Hook: If your engineering org is juggling Microsoft 365 licenses, slow manual conversions, and unreliable vendor APIs to produce PDFs and archives from Office files, this guide gives you a repeatable, auditable, and cost‑effective alternative for 2026: automating document conversion at scale with LibreOffice headless, CLI tools, and containerization patterns that replace M365 conversion workflows.

Executive summary — what you'll get

Most important first: this article shows production-ready patterns, runnable shell and Docker scripts, and CI/CD examples (GitHub Actions, GitLab CI) to convert, validate, compress, and archive Office documents. You will learn how to:

• Use LibreOffice headless (soffice) for reliable batch conversion (DOCX -> PDF, XLSX -> PDF, PPTX -> PDF).
• Integrate conversion into CI/CD pipelines safely (container-per-job, locking, concurrency controls).
• Validate PDFs (file type checks, PDF/A validation, basic accessibility and OCR fallbacks).
• Archive outputs with checksums, compression, and object storage.
• Handle failure modes, retries, and observability so you can replace Microsoft 365 conversion APIs in production.

Why LibreOffice headless matters in 2026

Since the mid‑2020s, companies have moved to self-hosted toolchains for data residency, privacy, and cost control. LibreOffice — maintained by The Document Foundation — continues to be the most mature open source option for Office format fidelity. Using LibreOffice headless in CI/CD reduces vendor lock-in, removes recurring conversion fees, and gives you control over audit logs, retention, and security.

Trend (late 2025–early 2026): IT teams prefer self-hosted conversion for compliance and cost; combining headless LibreOffice with containerization patterns is now a standard practice.

Architecture: high-level CI/CD pattern

Follow this pipeline model in your CI/CD system. The pattern is intentionally modular so you can run pieces in runners, Kubernetes jobs, or serverless containers.

1. Ingress: user or app drops Office files into a staging bucket or repo.
2. Trigger: object created event or commit triggers pipeline job.
3. Convert: run LibreOffice headless inside a controlled container; produce PDF(s).
4. Validate: run file checks, PDF/A validator (veraPDF) and optional OCR/QA.
5. Package: compress files, produce checksums, sign if required.
6. Archive: upload to object storage with lifecycle rules, or attach to release artifacts.
7. Notify: emit events/notifications and store logs/artifacts for audit.

Key constraints and operational notes

• Concurrency: LibreOffice can be stateful when launched without a user profile. Use container-per-job or a UNO listener pattern to avoid lock conflicts.
• Fonts: ensure the container has the fonts your docs use; mismatches cause layout drift.
• Performance: conversions are CPU and memory intensive; batch and parallelize intelligently using job queues.

Practical tooling: CLI commands you will use

The core conversion command is the LibreOffice soffice binary in headless mode. Complement it with small utilities for validation and packaging.

• Conversion: soffice --headless --convert-to
• Alternative converter: unoconv (wraps LibreOffice UNO)
• PDF normalization: ghostscript (gs -sDEVICE=pdfwrite)
• PDF/A validation: veraPDF
• File type checks: file and python-magic
• Checksums: sha256sum or openssl dgst
• Compression: tar + zstd
• Storage: aws cli, gcloud, or azcopy

Example Dockerfile: a minimal LibreOffice headless image

Use this image as the conversion runtime. It installs LibreOffice, fonts, and small utilities needed for validation.

FROM ubuntu:24.04
ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get update \
  && apt-get install -y --no-install-recommends \
     libreoffice libreoffice-writer libreoffice-calc libreoffice-impress \
     fonts-dejavu-core ghostscript file wget curl gnupg \
     python3 python3-pip zstd tar ca-certificates \
  && pip3 install python-magic
# Add veraPDF CLI (example: get binary from distro or include via package manager)
# COPY your-verapdf /usr/local/bin/verapdf
WORKDIR /workspace
ENTRYPOINT ["/usr/bin/soffice"]
  

Batch conversion script (robust, production-ready)

This script converts every Office file in an input directory to PDF, normalizes with Ghostscript, validates basic file type, writes checksum, and writes a JSON report. Run inside the Docker container or a CI job.

#!/usr/bin/env bash
set -euo pipefail
INPUT_DIR=${1:-/workspace/input}
OUT_DIR=${2:-/workspace/output}
LOG_DIR=${3:-/workspace/log}
mkdir -p "$OUT_DIR" "$LOG_DIR"
REPORT="$LOG_DIR/report.json"
printf '[' > "$REPORT"
first=true
for f in "$INPUT_DIR"/*; do
  [ -f "$f" ] || continue
  fname=$(basename -- "$f")
  base="${fname%.*}"
  echo "Processing $fname"

  # Check file type
  mimetype=$(file --mime-type -b "$f")

  # Convert to PDF
  soffice --headless --convert-to pdf --outdir "$OUT_DIR" "$f" || {
    echo "{\"file\":\"$fname\",\"status\":\"convert_failed\"}," >> "$LOG_DIR/errors.log"
    continue
  }
  pdf="$OUT_DIR/$base.pdf"

  # Normalize with Ghostscript (remove odd fonts, linearize)
  tmp="$OUT_DIR/$base.normalized.pdf"
  gs -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/printer -sOutputFile="$tmp" "$pdf"
  mv "$tmp" "$pdf"

  # Basic PDF/A validation (if veraPDF installed)
  if command -v verapdf >/dev/null 2>&1; then
    verapdf --summary "$pdf" > "$LOG_DIR/$base.verapdf.txt" || true
  fi

  # Checksum and record
  sha=$(sha256sum "$pdf" | awk '{print $1}')

  # Append to JSON report
  if [ "$first" = true ]; then first=false; else printf ',' >> "$REPORT"; fi
  jq -n --arg f "$fname" --arg p "$pdf" --arg m "$mimetype" --arg s "$sha" \
    '{file:$f, pdf:$p, mimetype:$m, sha256:$s}' >> "$REPORT"
done
printf ']' >> "$REPORT"
  

Notes on the script

• Use set -euo pipefail for safer failure modes.
• Ghostscript normalizes PDFs so downstream validators and archive readers see consistent output.
• Use veraPDF for formal PDF/A validation when archival compliance is required.

CI/CD examples

GitHub Actions: convert on push to a docs repo

name: convert-docs
on:
  push:
    paths:
      - 'docs/**'
jobs:
  convert:
    runs-on: ubuntu-latest
    container:
      image: ghcr.io/your-org/libreoffice-headless:latest
    steps:
      - uses: actions/checkout@v4
      - name: Convert documents
        run: |
          mkdir output log
          /workspace/convert.sh docs output log
      - name: Upload artifacts
        uses: actions/upload-artifact@v4
        with:
          name: pdfs
          path: output/*.pdf
  

GitLab CI: event-driven object storage conversion

convert_job:
  image: your-org/libreoffice-headless:latest
  script:
    - mkdir -p input output log
    - aws s3 cp s3://incoming-bucket/$CI_JOB_ID/ input/ --recursive
    - /workspace/convert.sh input output log
    - aws s3 cp output/ s3://archive-bucket/$CI_JOB_ID/ --recursive --storage-class STANDARD
  when: on_success
  tags:
    - linux
  

Concurrency and locking patterns

LibreOffice's UNO backend can conflict if two processes try to use the same user profile. Use one of these approaches:

• Container per job: spin a fresh container and run one soffice conversion — simplest and safest.
• UNO listener: run a long‑running LibreOffice listener process and connect multiple clients — efficient for many small conversions but requires a job queue and connection pool.
• File locking: use flock to serialize access to a central soffice installation (less recommended for scale).

Example: serialize with flock (if you must)

#!/usr/bin/env bash
LOCKFILE=/var/lock/libreoffice-convert.lock
exec 9>"$LOCKFILE"
flock -n 9 || { echo "Another conversion in progress"; exit 1; }
# safe to call soffice here
soffice --headless --convert-to pdf --outdir "$OUT_DIR" "$INPUT"

Validation: how to trust the output

For production workflows you need more than a successful exit code. Run a layered validation strategy:

1. File type check: file --mime-type.
2. Sanity checks: ensure PDF page count > 0, file size not zero.
3. PDF/A compliance: use veraPDF for archival PDFs.
4. Accessibility and text presence: check if PDF has text layer; otherwise run Tesseract OCR.
5. Metadata and redaction checks: run exiftool to inspect metadata and scrub if needed.

# Example quick validation
if ! file --mime-type -b "$pdf" | grep -q 'application/pdf'; then
  echo "Invalid output: not a PDF"
fi
pages=$(pdfinfo "$pdf" 2>/dev/null | awk '/^Pages:/ {print $2}')
if [ -z "$pages" ] || [ "$pages" -eq 0 ]; then
  echo "Empty PDF"; exit 2
fi
# veraPDF check (returns nonzero on failures)
if command -v verapdf >/dev/null 2>&1; then
  verapdf --format text "$pdf" > "$pdf.verapdf.txt" || echo "PDF/A check failed"
fi

Archival: compression, checksums, and storage

Archive with reproducibility and low cost in mind:

• Create a tarball of converted PDFs and include the JSON report and original files.
• Compress with zstd for speed and ratio.
• Produce a SHA‑256 manifest and optionally sign with GPG for provenance.
• Upload to object storage and apply lifecycle rules (warm/cold storage tiers).

# package and upload
cd output
tar -I 'zstd -T0 -19' -cf ../package.tar.zst .
sha256sum ../package.tar.zst > ../package.tar.zst.sha256
# Optional GPG sign
# gpg --detach-sign --armor --output ../package.tar.zst.sig ../package.tar.zst
aws s3 cp ../package.tar.zst s3://archive-bucket/releases/2026-01-18/ --storage-class STANDARD_IA
aws s3 cp ../package.tar.zst.sha256 s3://archive-bucket/releases/2026-01-18/

Failure modes and operational runbook

Expect and handle these common issues:

• Font substitution / layout differences — keep a font pack aligned with production editors.
• Large documents causing OOM — enforce memory limits and split big jobs or use streaming conversions for presentations.
• Non‑deterministic output — normalize with Ghostscript and store checksums of normalized artifacts.
• Incompatible Office features — log and fall back to human review for documents that fail fidelity tests.

Example mini case study (pattern you can adapt)

One mid‑sized SaaS firm replaced its 300-seat M365 conversion workflow: they moved conversion into an internal conversion cluster (Kubernetes) running the container above. Jobs were submitted via an SQS queue; each job spun up a single‑use pod, converted and validated files, and wrote artifacts to S3. Benefits realized:

• Predictable per‑conversion cost (compute + storage) vs. per‑seat licensing.
• Full audit trail: conversion logs and verapdf outputs stored alongside artifacts.
• Fewer support tickets because conversions became deterministic and reproducible.

Advanced strategies & future predictions for 2026

Looking forward, expect these directions:

• Hybrid AI validation: use model-based checks (summarization, layout comparison) to detect conversion regressions automatically.
• Serverless micro-conversion: faster cold-start containers and smaller LibreOffice runtimes will reduce cost-per-job.
• Policy-driven redaction: combined pipelines that run PII checks and automated redaction before archive.
• Open standards: more orgs will require PDF/A or PDF/UA compliance; veraPDF and automation will be mandatory stages.

Checklist: production readiness

• Container image with pinned LibreOffice version and fonts.
• Single‑use containers or enforced locking for concurrency.
• Validation pipeline: file-type, page checks, veraPDF, OCR fallback.
• Packaging: zstd tarball, sha256 manifest, optional GPG signature.
• Storage: lifecycle policy and retention rules in your object store.
• Monitoring: job metrics, error rates, and sample diffs to detect regression.

Actionable takeaways

• Start small: convert a subset of documents in a staging bucket to validate fidelity.
• Automate validations early: add file-type and page-count checks to fail fast.
• Containerize and pin versions: avoid surprise behavior from LibreOffice minor upgrades.
• Use artefact signing and lifecycle policies to meet compliance needs.

Closing thoughts

Replacing M365-based conversion with a self-hosted pipeline built around LibreOffice headless is realistic and production-ready in 2026. The combination of containerization, robust validation (veraPDF, ghostscript), and standard archival practices gives you cost control, privacy, and reproducible outputs — all critical for DevOps teams managing document workflows at scale.

Next steps: clone a starter repo with the Docker image and scripts, run a conversion test on a small sample, and expand the validations you need for compliance.

Call to action

Want a starter repo with Dockerfiles, CI examples, and a turnkey conversion pipeline tuned for your environment? Contact our integration team or download the starter kit to run your first batch conversion in under an hour.

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