Most PDF accessibility tools advertise speed without numbers. We ran our production engine — the same one behind our free checker and paid auto-fix — on a controlled set of documents and timed every stage. Here are the real measurements.
Methodology
We generated synthetic, text-heavy PDFs of 1, 10 and 50 pages (each page: one heading line plus 30 text lines, standard Helvetica, no images). Each document was run through three production stages on our EU hosting: the free accessibility check (veraPDF), PDF-to-Markdown conversion, and the paid auto-fix pipeline (auto-tagging plus a veraPDF re-audit). Small documents were timed over multiple runs; we report typical values. Your documents will differ — scanned pages, complex layouts and embedded fonts all change the picture — but the shape of these numbers is what you can expect.
Measured results
| Document | Free check (veraPDF audit) | Convert to Markdown | Auto-fix (tag + re-audit) |
|---|---|---|---|
| 1 page (4 KB) | 4.5 s | 2.3 s | — |
| 10 pages (37 KB) | 6.5 s | 6.8 s | 10.9 s |
| 50 pages (187 KB) | 7.1 s | 19.4 s | — |
What the numbers mean
The check has a fixed startup cost. veraPDF runs on a JVM that takes roughly 4 seconds to start and load its validation model. That is why a 1-page audit takes 4.5 seconds while a 50-page audit takes only 7.1. The marginal cost is about 0.02 seconds per page — the audit itself is extremely fast once the engine is warm.
Conversion throughput averages ~3 pages per second. Between the 10-page and 50-page runs, each additional page cost about 0.3 seconds — consistent with the throughput figure we publish on our homepage. A typical 20-page report converts in around 10 seconds.
Auto-fix costs roughly a second per page. The 10-page document was tagged and re-audited in under 11 seconds end-to-end. Our "about 60 seconds" guidance for a fix is deliberately conservative: most documents finish well ahead of it.
Honest caveats
- Scanned PDFs are a different workload. OCR adds seconds per page and can dominate everything else.
- Layout complexity matters. Tables, multi-column text and embedded fonts slow both conversion and tagging.
- These are server timings, not your stopwatch. Upload time, queueing and download add a few seconds in the browser.
- Auto-fix handles structure, not judgment. Alt-text quality and reading-context decisions still need human review — that is why every fix ships with a manual-review checklist.
Try it on your own document
The free accessibility check runs the same veraPDF engine measured above — upload a PDF and you will have a graded report in under ten seconds. If the document fails, the auto-fix is $2.99 per document, credits from $0.67, no subscription.