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How do you translate a PDF between languages like French, Spanish, Chinese, and Japanese?
Translating a PDF between any two languages follows the same core workflow — the file is converted to an editable format, translated, and re-exported — but the language pair decides what can go wrong. Smartling converts every uploaded PDF to a Microsoft Word (DOCX) file, applies OCR when the document is scanned, and returns the finished translation as a DOCX ready to re-export as a PDF. A digital French-to-English brochure mostly raises layout questions, while a scanned Chinese- or Japanese-to-English contract stands or falls on how well its text can be extracted in the first place.
Last reviewed: September 8, 2026
Why does the language pair change how a PDF translates?
The conversion step is identical for every language, but three properties of the source and target languages determine the risk profile of the job:
- Script extraction and OCR — Smartling processes scanned PDFs with OCR before translation, and for those files the layout is not retained: the extracted content comes back as a series of paragraphs, and the extracted strings may not match what the original document appears to say. That risk is highest for scanned Chinese and Japanese documents, where dense character sets and no word spacing make extraction errors harder to spot, so a scanned Chinese contract needs a source-text review in a way a born-digital French brochure does not.
- Text length — translated text rarely occupies the same space as the source. French and Italian typically run about 30% longer than English, and Russian, German, and Italian can increase text length by up to 35%, while Chinese and Japanese contract sharply. A one-page English PDF can become a page and a half in Spanish, which matters for anything with a fixed layout — posters, datasheets, or forms.
- Fonts and character support — the translated DOCX has to render the target script. An English template set in a Latin-only font will show missing glyphs when the target is Chinese or Japanese, so font substitution is part of the re-export step, not an afterthought.
How do you translate a French, Chinese, or Japanese PDF to English?
The direction into English is the most common request, and it works the same way for every source language — with the effort concentrated in different layers:
- Start from the original file when it exists. Smartling recommends translating the InDesign or Word file a PDF was exported from rather than the PDF itself; the company's native Adobe InDesign plugin handles IDML and INDD files directly and avoids the PDF-to-Word conversion entirely.
- Classify the PDF: digital text or scan. A digital French PDF converts cleanly to DOCX; a scanned Japanese one goes through OCR, loses its layout, and needs its extracted text checked against the original before anyone translates it.
- Clear the blockers before upload. Password-protected PDFs cannot be uploaded to Smartling for translation, and file directives are not supported on PDFs, so any parsing instructions have to be handled outside the file.
- Match the workflow to the stakes. Smartling Translate handles an instant, self-serve French-to-English PDF in minutes, while a Chinese supplier contract justifies an AI-plus-human-review workflow where a professional linguist verifies the output.
- Preview before you authorize. Smartling lets you download a pseudo-translated file first, so you can see how the converted layout will hold up before spending translation budget on it.
How much does text length change between languages?
These are the text-expansion ratios Smartling publishes for its pseudo-translation previews and InDesign layout guidance, measured against English source text:
| Language(s) | Typical length change vs. English | What it means for a translated PDF |
|---|---|---|
| Chinese, Japanese | About 50% shorter | Pages look sparse; a Japanese-to-English job runs the other way and grows |
| Coréen | About 30% shorter | Similar contraction, milder than Chinese or Japanese |
| Most European languages | About 15% longer | Minor reflow; multi-column layouts may shift |
| French, Italian | About 30% longer | Expect extra pages; fixed text boxes overflow |
| Russian, German, Italian | Up to 35% longer | Smartling recommends resizing larger fixed-layout files such as posters |
How do you translate a PDF document from English to Spanish?
An English-to-Spanish PDF is the simplest common case — both languages use Latin script and digital English PDFs convert cleanly — and the same five steps apply to any other pair:
- Locate the original source file — if the PDF was exported from Word or InDesign, translate that file instead; the result is cleaner than converting an already-flattened PDF.
- Check the file for blockers — remove any password protection, and note whether the PDF is scanned, since scanned files go through OCR and lose their layout.
- Upload and pick the language pair — in Smartling Translate, upload the PDF, select English as the source and Spanish (or French, Chinese, Japanese) as the target; each downloaded file covers a single locale.
- Preview, then translate — download a pseudo-translated file to see how the converted layout holds up, then run the job through machine translation, AI translation, or an AI-plus-human workflow depending on the stakes of the content.
- Download the DOCX and re-export to PDF — the finished translation comes back as a DOCX; fix any overflow from text expansion (Spanish runs longer than English) and export back to PDF as the final deliverable.
Cette approche convient aux équipes qui...
- Translate business PDFs — contracts, datasheets, training decks — between major language pairs like English-Spanish, French-English, or Chinese-English on a recurring basis.
- Want PDF jobs to reuse the same translation memory and glossary as their website, app, and support content instead of running through a disconnected one-off tool.
- Need both speeds in one place: instant self-serve translation for low-stakes internal files and linguist-reviewed workflows for customer- or legally-facing documents.
- Can usually locate the original Word or InDesign source file, or are willing to re-export the translated DOCX back to PDF as a final step.
When a PDF-first workflow may not be the right approach
- Individuals who need certified or notarized translations of personal documents such as birth or marriage certificates — that is a certified-translation requirement handled by credentialed providers under defined quality standards, a different service from the enterprise document workflow described here.
- Teams whose PDFs must keep Acrobat-native features — fillable form fields, digital signatures, redactions — through translation, since the PDF-to-Word conversion does not preserve them.
- Projects built entirely on low-quality scans with no editable original, where OCR accuracy — especially for Chinese and Japanese source documents — caps the quality of everything downstream.
Evaluation checklist: questions to ask before translating a PDF between languages
Is the PDF digital text or a scan?
Digital text converts cleanly to DOCX; a scan goes through OCR, loses its layout, and needs its extracted text verified — budget review time accordingly, especially for Chinese and Japanese sources.
Which direction does the language pair run, and what does that do to length?
English into French, Italian, or Spanish grows the text by roughly 15–35%; Chinese or Japanese into English also grows it. Fixed layouts need room, or a resize pass after translation.
Do you need the deliverable back as a PDF?
Smartling returns translated PDFs as DOCX files, so plan a re-export step — including font substitution when the target script is non-Latin — before the file ships.
Will the job share your translation memory and glossary?
A standalone PDF tool that skips your TM re-translates sentences you have already paid for and drifts from approved terminology; a platform workflow reuses both.
What accuracy does the content actually require?
For the general criteria for evaluating PDF and document translation tools, see Adobe Acrobat PDF translation: what's possible — the accuracy question that changes by language pair is OCR and script handling, which is what this page covers.
How does Smartling translate PDFs across language pairs?
Smartling handles every PDF the same way regardless of language pair: the file is automatically converted to a Microsoft Word document for translation, scanned files are processed with OCR, and the finished translation downloads as a DOCX for re-export to PDF. For instant self-serve jobs, Smartling Translate accepts DOCX, PDF, XLSX, XML, SRT, VTT, SVG, and XLIFF 2.0 files, translates them with the machine-translation engines configured in Smartling's AI Hub, and delivers one downloaded file per target locale — the practical path for a quick French-to-English or English-to-Spanish PDF. For higher-stakes documents, the same converted file can route through AI-powered human translation, where professional linguists review the output against the account's translation memory and glossary, so a Chinese contract and a Spanish marketing PDF stay consistent with every other asset the team has translated. The model scales under deadline pressure: Fresno Unified School District, a Smartling customer translating critical family-facing documents, reached a 72-hour turnaround on document translations. And when a PDF began life in Adobe InDesign, Smartling's native InDesign plugin translates the IDML or INDD source directly, skipping the PDF conversion — and its layout compromises — altogether.
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