How to make PDFs sharper (better readability)?

Question

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.

Answer 1

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.

Answer 2

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.

Answer 3

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

Answer 4

Thanks for the tip on IrfanView! I extracted the problem pages as sigle page PDF files and was able to open and edit them in IrfanView. I then replaced the bad pages in my PDF with the "optimized" pages.

I used Foxit Phantom PDF and was even able to go to File> Optimize Scanned PDF on the updated copy and it cleaned it up a little more.