Just an added note, I've heard most browsers are discontinuing any support for flash player mid-2019, which means that even if flash isn't totally dead until Dec 2020, it is effectively dead as soon as browser support stops.
And, commenting on the other posts, H5P is pretty good--much improved from the original version--and the Book module is also terrific. You could also do lesson, it remembers where you left off, which a pdf or Book won't (H5P might).