Straighten PDF (Deskew)

It renders each page small and measures how sharply the ink lines up into rows at every candidate angle within ±15°: level text piles into crisp rows, tilted text smears across them. The angle with the crispest rows is the correction. It works on anything with lines of text; a page that is mostly a photo reports no tilt.

No. The page content is wrapped in a rotation rather than re-rendered, so a scan keeps every pixel and vector text stays sharp; only the reader turns it. Bookmarks, labels and links survive too.

Turning a page's content leaves a thin triangle uncovered at each corner - the sliver every deskew costs. The page keeps its size; nothing of the text is cut off.

Nothing is uploaded: the file is opened and processed inside your browser and never leaves your device. Close the tab and it is gone.

Anything past 0.15 degrees is corrected; below that the page is left alone. That is about 1.5 points across the width of an A4 - under what the eye reads as crooked, and inside the measurement's own noise. So a straightened file fed back in is reported level rather than nudged again.

Yes. Select the pages and step the angle by tenths of a degree; the thumbnails show the corrected page as you go. "Reset" returns to what the measurement found.