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I've really badly scanned document in PDF which I would like to enhance (make grey, hardly visible invoice readable).

Is there some free tool, or trial tool that I could use on this one document?

OS is Windows.

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up vote 2 down vote accepted

Take a screenshot of it by Alt + PrtScr and paste it in IrfanView

Then go to the menu "Image" and apply "sharpen" ( or press Shift + s ) until you achieve the result you need.

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I tried both Shift + S and Shift + U and it seems Shift + U did it better. Tnx! – MadBoy May 16 '11 at 19:38

Cheapest would be to convert the pdf to an image. If you can fit the whole document on your screen without scrolling, just take a screenshot. Then use Irfanview or similar to adjust contrast and brightness to improve the file.

PDFs are not images per se, and so you cannot generally modify them, even with the full-blown pdf apps, like you would images, which is what you are trying to do in this process.

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Tnx. It was single page so screenshot was easiest to go. – MadBoy May 16 '11 at 19:38

As @music2myear has mentioned, taking a screenshot is not a good idea unless you can fit the whole image at 100% on your screen. Taking the screenshot of a smaller version will likely result in lower quality.

I'd suggest

  • extracting the images using XPDF (see this answer on how to do it)
  • and then opening it in IrfanView to sharpen
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