In nearly 20 years of its existence the PDF file format has become a staple on the majority of computers in the world. Its importance in document sharing grew from almost naught up to being the de facto standard on the Web. And the PDF software of choice for the most users has been and will be for a very long time par excellence Adobe Reader.
The current Adobe Reader 10.1 is no huge leap ahead in comparison with the previous releases. The most accurate description of it would be 'good old Reader'. However, it features a number of important changes involving mostly the commercially available features. So, now, using the Export PDF service, you can export your .pdf documents into .doc or .rtf format. However, this feature doesn't come for free: in order to enjoy converting the documents into an editable format, you'll have to fork out US$19.99, whereas there's a great chance that you'll find a nice freeware converter around.
Another important new feature that has been introduced recently is commentary adding that comes in two variants: sticky notes and text highlighting. Both of them will not shake the foundations of your ideas about software as they're practically identical to the corresponding features we're used to see in text editors like Word or LibreOffice.
The overall scarceness of really useful features in the free version is actually the greatest drawback of Adobe Reader. For example, unless you have acquired a yearly US$99.99 subscription, you won't have access to creating new PDF files. This strips Adobe Reader much of the efficiency it would have in our eyes if not for these exorbitant subscription fees. With so many alternative PDF-reading and converting applications around, it would be really hard for Adobe to keep up the competition.