Move and resize rectangular selections
After you draw a rectangular selection with Ctrl + drag, you can drag its edges or corners to resize it, or drag the inside to move it. This works like the crop rectangle in the image save/crop dialog.
Image thumbnail when dragging images out
When you drag an image out of a document, a thumbnail of the image with the right proportions follows the cursor, like in Chrome.
Engine DLL renamed to libsumatrapdf.dll
The companion engine DLL is now called libsumatrapdf.dll instead of libmupdf.dll. When upgrading from 3.6, the installer moves the old DLL aside.
SmoothScroll setting kept
Mouse-wheel scrolling is smoother, with less stutter. The SmoothScroll advanced setting is still there and now defaults to true. Set it to false for instant wheel steps.