When you create Smooth Scrolling pages in PDF Article Format, approximately the lower twenty percent of the Smooth Scrolling page enlarges. It doesn't display as expected on Web Viewer.
Some objects in the lower portion of the smooth-scrolling canvas appear to be enlarged or misshaped.
Create a smooth-scrolling canvas with dimensions that are exact multiples of the issue page size.
For example, if the page size is 768 x 1024 with vertical scrolling, make the smooth-scrolling canvas 768 x 1024, 768 x 2048, 768 x 3072, and so on.
Adobe is actively working on a permanent solution for this issue, and plans to incorporate a fix for this issue in future releases of Digital Publishing Suite.