Is there a way to enable smooth scrolling for PDFs?

Try holding alt when pressing the arrow keys.

Found it out today.

In Ubuntu 12.04 smooth scrolling is enabled system-wide and many GTK3 applications (most of the default ones) support it. However, the default PDF viewer, Evince, does not yet.

The good news is that smooth scrolling in Evince might be coming as an update. See https://bugs.launchpad.net/ubuntu/+source/evince/+bug/981248.

Also, if you disable overlay scrollbars, scrolling with the touchpad over the regular scrollbar will make the document scroll smoothly.

I find that opening the PDFs into Firefox (yes, the web browser) allows one to read them with smoothscroll. I have been unable to find a native/dedicated pdf viewer application for Ubuntu that does this.

I also found that I could solve Firefox's jerky smooth scroll by disabling all speedstep/power-saving related options in my BIOS.

Alternatives

If you hold down the middle mouse button and drag up/down, then that is a way to scroll smoothly. However, unlike with Firefox, you have to worry about the fact that you are not locked on the x-axis if you are zoomed in such that the margins do not show. The same effect can be realized by using Okular and just click-dragging rather than using the middle mouse button. This feels more natural.

Well unfortunately I cannot find anyway to directly fix the problem with the overlay scroll bars.

But have found a way to remove them so reading PDF's would again be possible. revert to the default scrollbarsecho "export LIBOVERLAY_SCROLLBAR=0" | sudo tee /etc/X11/Xsession.d/80overlayscrollbars > /dev/null

Found the solution here on Disable Overlay Scrollbars in Ubuntu Natty - TuxGarage