Deskew PDF

1. Choose your scanned PDF, or drop it onto the box. It opens in your browser, so the file never leaves your device.
2. Let the tool measure each page. It finds the lines of text on every page and works out how far they lean. The small page buttons show the result, such as 3 · ↻ 1.6°.
3. Check the preview. The blue guide lines are level, so the lines of text should run along them. If a page is still off, drag the slider or type an angle.
4. Download the straightened PDF. The button says how many pages will be turned, for example Straighten 7 pages and download. You get a copy named yourfile-straightened.pdf; the original file is not changed.

Pages that already look straight are left exactly as they were. The tool corrects tilts of up to 15° either way.

A scan is a photo of the page, so if the paper wasn’t square to the scanner, the text leans in the picture. The usual causes:

• The document feeder pulled the paper in at an angle. Thin receipts, mixed paper sizes and loose guides are the main culprits. The whole batch often leans by the same amount.
• The page was placed on the glass by hand and wasn’t lined up with the edge.
• It was photographed with a phone that wasn’t held level over the page.
• The original was printed or photocopied crooked, so even a perfect scan of it leans.

Straightening matters for more than looks. Crooked text is harder to read and print, and text recognition (OCR) makes more mistakes on it, because it reads the page one line at a time.

The automatic measurement works from lines of text, so it is reliable on letters, invoices, forms and book pages. Check these pages by eye:

• Photos and drawings have no neat lines to measure, so the tool leaves them alone. Use the slider and line up an edge you know should be level, such as a table border or the edge of a photo.
• Handwriting rarely runs perfectly level, so check those pages by eye and nudge the angle if needed.
• A whole batch leaning the same way: set one page right, then click Use … on every page to give every page the same angle.
• A page that is sideways or upside down is not crooked. It needs a quarter or half turn, which is more than this tool corrects.

No. The tool turns what is already on each page instead of taking a new picture of it. The scan keeps its original sharpness and file size, and any text you could select or search before (including text added by OCR) turns with the page and still works.

Two things to be aware of:

• The corners are trimmed slightly. The page keeps its size, so turning the content pushes a thin sliver past each corner and leaves a small white wedge at the others. On an A4 or Letter page turned by 2°, that is about 4 mm at the corners, usually just empty margin.
• Links and form boxes stay where they were. They don’t turn with the page, so on a turned page they can be a few millimetres off what they belong to.

If the PDF was digitally signed, the straightened copy no longer has a valid signature, because the file has changed. The tool warns you when it finds a signature.