A sheet pulled through a feeder arrives a degree or two out of true, and a page photographed on a phone can be worse. The eye adjusts; text recognition does not, which is why skew is one of the commonest causes of garbled OCR — and nothing looks more slapdash in a bound report. Each page is rendered small and measured the way a typesetter would: the ink is projected onto the vertical axis, and the angle at which the lines of text stack up most sharply is the tilt. That angle, and how clear the measurement was, sits next to a thumbnail of every page, and you can overrule any of it before rebuilding. The straightening itself is geometry rather than pixels — pages are redrawn rotated about their own centres on your device.
Features
Every page is measured on its own, so a stack that drifts page by page is handled page by page
The detected angle and a confidence badge sit beside a thumbnail of each page
Pages tilted less than a tenth of a degree, or measured with little confidence, are left out by default
Type your own angle for any page, in steps of 0.05°
Straightening is lossless: the page is redrawn rotated, so text stays selectable and images keep their quality
Optional slight shrink so a turned corner is not clipped by the edge of the sheet
Pages you leave alone are copied across untouched, with their links and form fields
The straightened document is previewed in the page before you download it
How to use the Deskew PDF
Drop the scanned PDF — each page is rendered and measured as it loads
Read down the grid: the angle, the confidence, and whether the page is included
Change any angle, or tick a page you want straightened anyway
Straighten, check the preview, and download the corrected copy
minutes-scanned-deskewed.pdf — pages 1 and 3 turned back level, page 2 copied as it was
Only the pages that need it are rebuilt, so the rest keep everything they had.
Common errors & troubleshooting
A page is marked unsure and left out of the selection. — There was too little text on it to measure — a photograph, a signature page, a nearly blank sheet. Read the angle off a neighbouring page and type it in, or leave that page alone.
A corner of the content is clipped after straightening. — Turning a page swings its corners outwards, past the edge of the sheet. Switch on “Shrink slightly so no corner is cut off” and rebuild: the content lands a few per cent smaller and complete.
The page was sideways or upside down, and nothing improved. — That is a quarter or a half turn, not skew — only tilts up to ten degrees are measured as skew. Use Rotate PDF for the big turn first, then come back for the fine correction.
Links stopped working on the pages that were straightened. — A rebuilt page keeps its content but not its annotations. Straighten only the pages that need it — every other page is copied with its links intact — or add the links again afterwards.
Frequently asked questions
How is the tilt of a scanned page actually measured?
The ink is counted row by row at a series of trial angles. On a level page the lines of text make sharp peaks with empty gaps between them, and tilt smears those peaks together, so the angle with the sharpest peaks is the skew. It is refined in steps of 0.05°.
Does straightening a scan re-compress it?
No. The page is embedded exactly as it is and drawn onto a new sheet through a rotation, so the original image data is reused byte for byte, and any real text on the page stays selectable and searchable.
Is half a degree of tilt worth correcting?
For reading, no. For text recognition, yes: half a degree is invisible on screen and still enough to make a line of characters wander across pixel rows, which is where recognition starts guessing.
What if two pages need opposite corrections?
That is the normal case for a stack fed by hand. Each page carries its own measured angle and its own page box, and the rebuild applies them one at a time.
Can I turn a page the measurement says is already level?
Yes. Tick the page and type the angle you want; anything up to 45 degrees either way is accepted, in steps of 0.05, whatever the detected value was.
Related tools
PDF OCR — Recognise the text in a scanned PDF and make it searchable.
Scan to PDF — Use a camera as a document scanner and save the pages as a PDF.
Rotate PDF — Rotate all pages or a selection by 90/180/270°.
Crop PDF — Trim margins from every page via the crop box.
Blank Page Remover — Find and delete blank pages from a scan, with a tolerance you control.
PDF to TIFF — Render PDF pages into a multi-page TIFF in colour, greyscale or black and white.
Make PDF Look Scanned — Give a digital PDF the tilt, grain and grey tone of a page that went through a scanner.
More PDF tools
Image to PDF — Combine images into a single PDF (auto / portrait / landscape).
PDF to Images — Render PDF pages to PNG or JPG images you can download.
Merge PDFs — Combine multiple PDFs into one, with reordering.
Split PDF — Extract pages or ranges (e.g. 1-3,5,7-9) into a new PDF.
Rotate PDF — Rotate all pages or a selection by 90/180/270°.
Organize PDF — Reorder, rotate and delete pages from thumbnails, then export.
Add Page Numbers — Stamp page numbers onto a PDF (position, format, start).
Watermark PDF — Add a diagonal text watermark to every page.
Crop PDF — Trim margins from every page via the crop box.
PDF to Text — Extract selectable text from a PDF as plain text or Markdown.
Compare PDFs — Diff the extracted text of two PDFs line-by-line.
Encrypt PDF — Password-protect a PDF with AES-256 or RC4 encryption.
Decrypt PDF — Remove password protection from an encrypted PDF.
Compress PDF — Shrink a PDF by re-rendering each page to a JPEG at a chosen quality and resolution.
PDF Metadata Editor — View, edit or strip a PDF’s title, author, subject, keywords and producer.
Resize PDF — Rescale every PDF page to A4, Letter or another standard size, content centred.
Flatten PDF — Lock filled form fields into the page so a PDF looks the same everywhere.
PDF N-up — Print 2, 4, 9 or 16 pages per sheet, with a booklet option for folding.
Interleave PDF Pages — Merge odd and even scan passes back into one document, reversing if needed.
PDF to Single Long Page — Stack every page onto one continuous sheet you scroll instead of paging.
PDF Form Data Extractor — Pull the answers out of a filled PDF form as JSON or CSV, field by field.
Blank Page Remover — Find and delete blank pages from a scan, with a tolerance you control.
Text to PDF — Turn typed or pasted text into a paginated, downloadable PDF.
Markdown to PDF — Render Markdown — headings, lists, tables and code — as a PDF.