Deskew Scanned PDF — Auto-Straighten Tilted Pages
Detect and correct skew on each page of a scanned PDF — useful for documents fed through a scanner crooked or photographed at a slight angle. Each page is converted to an image, rotated to upright, and re-embedded. Free, in-browser, and no signup — your file stays on your device.
Free • No signup • Secure
How to use deskew scanned pdf — auto-straighten tilted pages
Open your scanned PDF
Drag and drop your PDF onto the upload area, or click to choose a file. The file stays on your device — there is no server upload.
Detect the skew angle on each page
USA Sky PDF renders every page at 1.5× resolution in your browser and runs a projection-profile skew detector. The algorithm sweeps a range of candidate angles and picks the one that maximises horizontal text-band contrast — accurate to roughly ±0.25° on typical scans.
Rotate each page to upright
Each page is rotated by the inverse of its detected angle on a sized-to-fit canvas (so corners aren't clipped), then saved as a JPEG. Pages with skew under 0.1° are left untouched.
Download the deskewed PDF
Click Deskew Scanned PDF to save the corrected .pdf to your device. You can run OCR on the output afterward to make the text searchable.
Why use USA Sky PDF
Your file stays on your device
Nothing is uploaded. The deskew runs entirely in your browser, and the new file is saved straight to your downloads folder.
Projection-profile skew detection
The standard algorithm for document deskew — sweep candidate angles, score each by horizontal text-band contrast, pick the winner. Accurate to roughly ±0.25° on typical scans without needing per-document tuning.
Sized-to-fit output canvas
When the rotation is large (5°+), corners of a same-size canvas would get clipped. The tool sizes the output canvas to the rotated bounding box so no content is lost — important for pages that are skewed near the limit.
Cancellable mid-run
Long scans (100+ pages) can be cancelled while running — the partial result up to that page is discarded, no upload to clean up.
Frequently asked questions
Is deskew really free?
Yes. Free with no signup and no per-conversion limit.
Does the file leave my computer?
No. Deskew runs entirely in your browser. USA Sky PDF's servers never see your PDF for this tool.
Does this work on born-digital PDFs?
Not really. Born-digital PDFs — Word exports, LaTeX, web PDFs, PDFs from any modern app — aren't actually skewed at the pixel level; their vector text is upright in the content stream regardless of how the page is rendered. Running deskew on those will either find a roughly-zero angle (no-op aside from the destructive image conversion) or pick up a spurious angle from canvas-rendering artefacts. If you need a quarter-turn rotation (90 / 180 / 270 degrees), use /rotate-pdf instead — that's lossless and metadata-only. Deskew is specifically for scanned documents where text is genuinely tilted at the pixel level.
Will text still be selectable after deskew?
No — same as Flatten and Grayscale, the rotated pages are JPEG images. Scanned PDFs usually weren't selectable to begin with, so this is rarely a regression in practice. If you need searchable text on the deskewed output, run OCR on it afterward to add an invisible text layer.
How is the skew angle detected?
Projection-profile method. The page is rendered, candidate angles in a range around 0° are tried, and the one that produces the strongest horizontal text-band contrast wins. This is the standard document-deskew algorithm and works without per-document tuning. Accuracy is roughly ±0.25° on text-heavy scans.
What if a page isn't actually skewed?
Pages with detected skew under 0.1° are left at their original orientation — no destructive image conversion happens on those pages. They still get re-embedded as JPEG (because we re-build the document), so the file format trade-off still applies.