I have always used Snagit for screen captures, it has nice workflow and just works. Except for the last two years it does not work properly if you have a high dpi monitor such as Microsoft Surface. In my case I have an external monitor as well and the Snagit interface becomes tiny on the Surface. When you move the window from monitor to monitor it does not scale nicely. Lots of software has problems with high DPI monitors but this is their core business so it is particularly annoying.
I routinely upgrade and I have just bought Snagit 2018. They have not fixed the high dpi issues but have added OCR. This has been available in OneNote for a long time.
I will now start thinking about a OneNote and Paint workflow to produce training documents. This is cheaper for me as a single user, and certainly cheaper at scale for schools.