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Deskew PDF Scans
Deskew PDF Scans measures how far each scanned page is tilted and straightens it. The tool scores candidate angles between -6° and +6° by looking at how strongly the ink rows line up, then rebuilds each page rotated by the winning correction.
How to use Deskew PDF Scans
- Upload the skewed scan or photographed pages.
- Run the tool; each page is measured across a range of candidate angles.
- Download the straightened document and check that text baselines now sit level.
Where Deskew PDF Scans is useful
- Straightening pages from a sheet-fed scanner that did not grip the paper straight.
- Fixing phone photos of documents taken at a slight angle.
- Tidying faxes and photocopies before archiving them.
Formats, algorithms and limits
Skew is estimated with a projection-profile method: the page is rotated by each candidate angle and the angle that produces the sharpest row-to-row variation in dark pixels is chosen. Because the correction is applied by re-rendering, the output pages are images — which is also why the method copes with photographs of paper.
Troubleshooting and honest limits
- The search range is ±6°, which covers normal scanner skew; bigger rotations need the Rotate tool.
- Bent or curled pages cannot be fixed by rotation alone.
- Check the result if a page contains diagonal design elements — the algorithm assumes text runs horizontally.
Frequently asked questions
How does the tool decide the skew angle?
It tries angles in half-degree steps and keeps the one where dark pixels concentrate into the fewest, crispest horizontal bands, which is the mathematical signature of level text.
Why do the pages become images?
Straightening requires rotating the rendered pixels. Re-rendering guarantees the correction is baked into the output instead of being a view setting.
Can it deskew a document that is rotated 90 degrees?
No. The search range covers small tilts only; use Rotate PDF for quarter-turn corrections first, then deskew.
What happens to a page that is already straight?
The measured angle is zero, so no rotation is applied and the page is simply re-saved.
Related tools
Page written and reviewed by the FreeConvertio engineering team on 2026-10-14. Deskew PDF Scans runs entirely in your browser — no uploads, no account and no daily limits.