This update has two main changes: a big improvement for startup performance, and availability on the Windows Store. The “Classic” release is still available, of course, and will continue to be updated and maintained on roughly the same schedule as the Store release. I will be publishing another blog post discussing the Store release very soon (edit: here you go).
As usual, you can download the update directly from the website, or you can use the built-in updater via Settings –> Updates –> Check Now. You can also purchase it from the Windows Store, in which case updates will become completely automatic and you’ll never have to worry about it ever again 
Here’s the official changelog:
- Improved: Startup performance has been improved by about 25%
- New: Now available on the Windows Store! https://www.microsoft.com/store/apps/9NBHCS1LX4R0
- Improved: Plugins can now be installed per-user into “Documents\paint.net App Files” into folders named Effects, FileTypes, and Shapes. This is required for using plugins with the Store release. To disable this (e.g. for administrators), set the “Plugins/AllowLoadingPluginsFromUserLocations” key to “false” (HKLM\Software\paint.net).
- Improved: When using Portable Mode, custom palette files are stored next to the EXE instead of in Documents
- Fixed: There was a crash on some systems that may have prevented the app from starting up (MissingMethodException for “System.GC.Collect”)
Enjoy!
paint.net blog 
hahaha agora ta entrando mais rápido no paint-net
falei errado ta entrando mais rápido com paint net
antes tava demorando muito para entra vlw
> “Plugins can now be installed per-user into “Documents\paint.net App Files”
LOL. So, you too joined the ranks of bad developers who pollute the “Documents” folder. 😉
Don’t worry. I have long gotten used to the fact that “Documents” is a secondary dumping ground for application data. In fact, I suspect what I said and what you did are cause and effect.
Every now and then, I rename the folder to “Not Documents!”. (It gets reverted after a Windows update.) I used to rename it to other … contemptuous names. 😈
Unfortunately it’s the only location that works for the Store release. Every other location gets virtualized in ways that don’t work or even make sense (for the user at least).
“paint.net App Files” is only there if you create it, or if the Store version needs to dump a crash log somewhere.
Yep. Like I said: Cause and effect.
It is another version of the old environmental pollution story many years ago: Generating pollution had become not only rampant, but also a norm, to the point that if industrial plants wanted to generate less pollution, they’d be severely punished. In that story, the law came in and solved the problem with fines and prison terms.
Of course, the pollution was killing the planet. “Documents” folder’s status is not killing anyone. Windows is dying on its own. 😜 (Yes, the last sentence was a joke, even though looking at Microsoft support policy, it seemed the Windows platform is scheduled for an ignoble death in 2020.)
Will Desktop version continue to be free?
Since the update I can no longer view the thumbnails of my images when looking in files, just the thumbnail icon. Is it possible to change it back? I can send a screenshot to explain better if required.
Same problem here 😦
4.0.19 fixes this. If you have the Store version, it is still on 4.0.18 but should be updated soon. https://blog.getpaint.net/2017/10/02/paint-net-4-0-19-is-now-available/