ArPDF — does Arabic survive a PDF?

Author: Syamjith NK Write-up: Your Arabic PDF is fine. What reads it is not. Third in a series with ArNum-TTS (speech) and ArShape (screen rendering).

The finding

No PDF generator and extractor pair reads Arabic reliably, and correctness depends on the pair rather than on either tool.

5 Arabic strings × 4 generators × 3 extractors. Clean extractions out of 5:

generator	pypdf	pdfminer.six	poppler pdftotext
Chrome (HTML → PDF)	3/5	0/5	1/5
ReportLab (naive)	0/5	5/5	0/5
ReportLab (+ reshaper)	3/5	0/5	3/5
LibreOffice (.docx → PDF)	5/5	0/5	2/5

Why pdfminer inverts

pdfminer is 0/5 against three generators and 5/5 against exactly one — the only one that performs no text layout. That is not a coincidence, and it explains the whole table.

ReportLab-naive writes the characters into the PDF in logical order, because it does no shaping or bidi. Chrome, LibreOffice and reshaped ReportLab all lay the line out visually first, so the PDF stores glyphs in visual order. pdfminer returns what is stored without re-applying bidi, so it is right precisely when the generator was naive. pypdf and poppler apply their own reordering heuristics, which is why they land in between.

So the question a PDF answers is not "is the Arabic correct" but "which order is it stored in, and does this reader re-apply bidi". No tool tells you either.

The two ends invert. ReportLab-naive extracts perfectly through pdfminer and fails every other reader; Chrome — the route most web tooling uses — is 0 for 5 through pdfminer, which is what many document pipelines run.

So you cannot choose a "good" PDF library or a "good" extractor. A document that survives one reader is unreadable to the next, and when you submit a PDF you do not control which reader is on the other side.

Why it matters

A PDF looks correct, so it is trusted. But almost nothing that consumes one looks at it — procurement portals parse the text, search engines index it, compliance tools scan for terms, applicant systems read CVs. All of them extract.

An Arabic tender response that renders perfectly on screen and extracts as reversed text is, to the system reading it, gibberish. Nobody involved sees the failure.

Three distinct failure modes

Counted separately, because they need different fixes and have very different blast radii.

mode	what happens	example
reversed	the whole string comes back in visual order, so it reads backwards	source مرحبا بكم في دولة الإمارات
		extracted تاراملإا ةلود يف مكب ابحرم
ligature	the lam-alef (لا) is one glyph in the PDF and returns as two letters in the wrong order	source الإمارات
		extracted اإلمارات
spacing	letters intact, word and number boundaries lost	extracted النسبة2026في

Observed across the matrix: 9 reversed, 17 ligature, 4 mangled.

The ligature mode is the dangerous one. It is subtle enough to survive a human proofread — a reader skims past اإلمارات — while still breaking exact-match search, keyword compliance checks and any automated comparison.

What this does NOT cover

Stated plainly, because it is the obvious next question:

• Microsoft Word itself, InDesign and LaTeX are untested. LibreOffice covers the .docx route because it is the dominant headless converter, but it is a different engine from Word and may lay text out differently. InDesign and LaTeX are not installed here, and WeasyPrint could not run (it needs Pango).
• One font (system Arabic) and one page layout. Embedded subsets and CID fonts may behave differently.
• Extraction only. It says nothing about whether the PDF renders correctly — it does.

Reproduce

python pdf_bench.py

Writes every generator × extractor combination to results.jsonl with the extracted text for each, so the failure modes can be inspected rather than taken on trust.

Does Arabic Survive the Pipeline?

This is one of three reproducible benchmarks, one per stage of a real production pipeline. Each measures an Arabic failure that looks correct to anyone who does not read Arabic — which is exactly why it ships.

• ArNum-TTS — do numbers survive speech synthesis?
• ArShape — does the standard reshaping recipe survive rendering?
• ArPDF — does Arabic survive a PDF round trip? → you are here

All three are CC BY 4.0 and ship the scorer, the raw per-item results, and an explicit statement of what the measurement does not establish.