In Acrobat DC you can create your own tool sets. Unfortunately you will have to open your tool set again EACH time a new PDF is opened.
Since it’s not possible anymore to collapse the tool sets (like in Acrobat XI) you either have to put all your tools in one large tool set (which requires frequent scrolling) or to create multiple tool sets. A change of the active toolsets requires another two mouse clicks.
The right hand pane with the tools which is quite large is always open when a PDF is opened. You will have to close it manually in order to get more screen real estate to display your document. On the other hand the left hand pane with the navigation panes which is much smaller is closed by default. It opens automatically if the PDF contains bookmarks or layers but not if the PDF is a standard PDF (e.g. PDF/X). In order to see if a PDF is a standard PDF you must first open the left hand pane (by clicking on a tiny arrow) and then you will have to click on the icon of the standard navigation tool. Another two unneccessary mouse clicks.
Compared to former versions more mouse clicks are required to get the same result. Adobe has some homework to do!