As usual, you can either use the built-in updater from the Utilities menu, or you can download and install directly from the website: http://www.getpaint.net/ . There’s no need to worry about removing the old version; that is all handled automatically.
This update fixes several issues related to copy-paste, improves performance and quality for a few adjustments, and fixes a data loss bug.
- When pasting an image, Paint.NET will be smarter about ensuring it is placed within the area that has been scrolled/zoomed to.
- Improved the performance and quality of the Curves and Hue/Saturation adjustments.
- Some minor improvements to memory usage, which should help out a few scenarios on 32-bit systems.
- Fixed: If a JPEG was loaded that had an embedded ICC profile, and was then saved as an 8-bit or 24-bit PNG, then the resulting file would be corrupt (32-bit PNG worked fine though).
- Fixed: 16-bit TGAs no longer load with the red and blue channels swapped.
- Fixed: Copy-paste from a Remote Desktop session will no longer be ‘shifted’ by 3 pixels.
- Fixed: Copy-paste from Internet Explorer, Firefox, or Chrome should preserve alpha/transparency.
- Fixed: Copying from Paint.NET and pasting into Windows Live Writer should now work.
- Fixed: Taking a full-screen screenshot with Print Screen on a multimonitor system, where those monitors don’t form a simple rectangle, will now fill the ‘gap area’ with transparent instead of black. (Example: two monitors of the same size, one of which is rotated by 90 degrees)
- Fixed: If Paint.NET is opened without specifying an image to open, and then the default image is modified and saved, then Paint.NET will no longer close it upon opening another one. This was causing data loss if that default image had layers, and was then saved in a format that did not support layers (anything other than .PDN).
- Fixed: Some systems were showing ‘red X’ thumbnails for .PDN files in Windows Explorer, instead of the real thumbnail.
- Fixed: The EXIF “Creation Software” saved along with images is no longer localized. This prevents certain languages from seeing “Paint.NET ????? v3.5.6” in the image properties (metadata).
Hopefully these fixes should make the wait for 4.0 easier to bare 
Also, as a bonus feature which is a corollary to how I’m now handling copy-paste from Internet Explorer: if you “copy” an image from Windows Explorer, you can paste it straight into Paint.NET. For example, right click on some stray image you’ve left on your desktop (c’mon we all have a cluttered desktop). Next, paste into Paint.NET. Pretty cool, maybe even useful.
paint.net blog 
Woohoo, great stuff! 🙂 Thank you for all your work, can’t wait to check out the update.
“When pasting an image, Paint.NET will be smarter about ensuring it is placed within the area that has been scrolled/zoomed to.”
A million, billion times I thank you. This was one of those simple things that was driving me nuts.
Nice, thank you for fixing issues related to Remote Desktop !
Fixed: Copy-paste from Internet Explorer, Firefox, or Chrome should preserve alpha/transparency.
Wow! That’s a life saver! I didn’t even know that was possible! (it goes wrong in any other programme too) Thanks a lot!
Thank you, Rick, for all of your hard work. I’m going to download it now. I’m becoming a regular visitor to the blog.
Kudos!
I am generally very happy with your program so thanks for all the effort. May I just add that the only thing that is lacking is the ability to manually rotate and distort proportionally.
I don’t understand what you mean by, “rotate and distort proportionally.”
WebP support?
Nope. Why don’t you write a plugin for it?
Thanks, Rick!
There are more bug fixes here than I expected. I especially like the hue and saturation improvements, and the bonus copy and paste feature. Good stuff Rick. 🙂
Very nice. I’ve been using PDN for a while now and it’s become one of my favourite tools. One thing that I think would be a great addition though is some sort of preferences options – default settings for tolerance, antialiasing, blending mode, blank canvas size… I use it for pixel art sometimes which means I have to adjust these things a certain way every time I start the program. Is this something you’d consider for the 3.x PDN, or will I have to hold on for Version 4?
When I found out that Pain.NET 3.5.6 preserved alpha/transparency when copying from a web browser, I was surprised. That is really cool and useful. I tried it out and it works with Internet Explorer, but it does not work with Google Chrome version 7.0.517.44 or 8.0.552.215. That alright, though. I am still really happy with Paint.NET. It is way faster and easier to use than GIMP. Great job!
Works on Chrome 8 here just fine.
It’s probably my computer. I’ll figure it out.
I’ve been using Paint.net for a few months and really like it. The only feature missing for me is an arbitrary angle rotation.
It sure would be nice if dialog boxes didn’t open right in the middle of the image. (I feel like a voice in the wilderness on this one…)