Sorry, you've saved the screenshot as JPG which means you have already created a lossy result.
When you paste the sceenshot into PS from the clipboard, it is raster (pure bitmap data) - make sure you resize and save using a lossless format
Printable View
Try using a dedicated program, there are so many of them that you can use, instead of Prt Scr. You will have much more control of your output.
None other than Photoshop.Its best software for high image resolution.