Microsoft has pushed out an update to their Reader app on all Windows 8.1 and Windows 10 PCs. The app is a very streamlined pdf file viewer that launched alongside the Windows 8 operating system and it remains one of the fastest and simplest ways to open pdf files, read them, and make annotations or signatures with the Surface Pen.
The Reader app had been seemingly abandoned by Microsoft after the launch of their Edge browser which the company attempted to make an all-in-one app for internet browsing, pdf reading, and (recently) ebook reading. Despite this though, it's still available as a free download in the Windows Store and is worth checking out.
The small update pushed out to the app today fixed some stability issues and some data-loss problems.