It depends on the original picture size (which is based on your screen resolution) versus what size of picture you're trying to print. For example, if your screen resolution is 1366x768 (720p) at 96 DPI (dots per inch - standard TV and monitor DPI), then it's quite a bit smaller than a US Letter size page at 300 DPI (standard printer DPI). So, your image has to stretch to fit and can look blurry or out of focus.
A decent photo editor can help re-size and reduce the blurriness, but in general you want to print a photo size smaller or near the same resolution as your screen. It's better to scale down your image rather than scale up. I use PhotoPlus from Serif, but there's also PaintShopPro from Corel and PhotoShop Elements from Adobe. Any of these will work well for resizing pictures for print. I would not spend the money for the full version of PhotoShop unless you are a photography student or a professional graphics designer, as it is overkill for everyday touch ups and very expensive.
Hope this helps.
Flynn
