Why Arabic text comes out backwards when you extract it from a PDF (and how to fix it)

If you've ever built a feature that extracts text from PDFs, an Arabic-speaking user has probably filed this bug: "the words come out in reverse order." Not the letters — the words . Every line reads last-word-first. I spent the better part of a year fixing this class of bugs while building Confileo , a free PDF toolkit with first-class Arabic support. Here's what's actually going on, because almost every explanation online is wrong or incomplete. The four distinct failure modes People say "Arabic breaks" as if it's one bug. It's four: 1. Visual vs logical order (the reversed-words bug) A PDF doesn't store text the way a Word file does — it stores positioned glyph runs : "paint these shapes at these coordinates." For left-to-right scripts, the paint order happens to match the reading order, so naive extraction works by accident. Arabic is right-to-left. Many PDF generators emit the glyph runs in visual order — the order they appear on screen, left to right. A naive extractor concatenates the runs as stored and produces every line word-reversed. The text was never "reversed" in the file; your extractor just assumed paint order == reading order. Fix: reconstruct logical order using glyph positions + the Unicode Bidirectional Algorithm (UAX #9), not the content-stream order. Libraries like PyMuPDF already return text in logical order — a common mistake is "fixing" that output by reversing it again, which is how you get double-reversed text. Rule of thumb: never reverse Arabic yourself. If it looks backwards, your rendering layer lacks bidi support; the data is usually fine. 2. Disconnected letters (the ransom-note bug) Arabic letters are contextual: ع renders differently in initial, medial, final and isolated positions, and letters join. That joining is applied at render time by a shaping engine (HarfBuzz being the standard). If any step of your pipeline round-trips text through a non-shaping renderer — a canvas library, a barebones PDF writer, an image caption filter