Paint.NET is a graphics creation and photo-editing application designed as an alternative to Microsoft Paint. Paint.NET features a far more complex range of capabilities than the built-in Windows alternative, including many tools that professional-grade photo-editing software such as Adobe Photoshop features. If you want to fix a blurred photograph, then you can use the "Sharpen" tool in Paint.NET. Sharpen will not fix a badly blurred image, but if there is slight blurring, then sharpen should fix the edges enough to make the image presentable.
Double-click the "Paint.NET" application on your desktop.
Press "Ctrl" and "O." Locate then double-click your photograph for editing.
Click "Effects" and select "Sharpen."
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Move the "Sharpen" slider to the right to increase your sharpening. Sharpening increases the edge definition and thus reduces blurred effect. Click "Sharpen" when you are happy with how your image looks.