Fix a blurry PDF

How to fix a blurry PDF

1. Pick how soft the page looks above. Soft is selected to begin with.
2. Choose your PDF, or drop it on the page. It is processed in your browser and never uploaded.
3. Zoom in on small text and drag the slider to compare the original with the result.
4. If edges still look smeared, choose a stronger setting or raise Blur size. If they look rough or grainy, lower Sharpening amount. Then press Apply new settings.
5. Download the new PDF. The original is left untouched.

What actually helps a blurry page

• Sharpening steepens the soft edges so strokes look crisper. It is limited so it cannot draw halos around letters.
• Blur size tells the sharpening how wide the soft edges are. A page that is only a little fuzzy needs a small value; a page smeared across many pixels needs a larger one. Too large a value on a sharp page makes it look rough.
• Contrast widens the gap between ink and paper, which helps blurred strokes stand out from the background.
• Text darkness pushes grey, smeared ink towards black, which makes thin blurred strokes read as solid.

What it cannot do

• It cannot add resolution or invent detail. A tiny, low-resolution image stays low resolution.
• It cannot undo motion blur or heavy out-of-focus blur. Strong sharpening on those pages produces rough, artificial edges instead of readable text.
• It cannot read text that is no longer legible. If a page is still unreadable on the strongest setting, rescan it, ideally at 300 DPI.
• It does not use AI upscaling, and it does not read the text. OCR a scanned PDF does that.
• It cannot tell you how blurry a page is. Blur is not measured, so you choose the setting by comparing the result.

Soft scan, low resolution, or motion blur?

The kind of blur decides how much a tool can help.

• A slightly soft scan — edges are a little wide and everything else is fine. This responds well to sharpening.
• A low-resolution image — the letters are made of visible blocks. Sharpening makes the blocks harder, not the letters clearer. Contrast and darkening still help readability.
• Motion or focus blur — the whole page is smeared in one direction or everywhere. Only a mild improvement is possible.
• If the original paper is still available, scanning it again at 300 DPI will beat any amount of processing.

Which pages are changed

Pages that contain images, including every scan, are rendered at 200 DPI, processed and written back as images. Pages made only of text and vector graphics cannot be blurry in this sense, so they are left untouched, and the result panel tells you when that happens.