epdfview and/or zathura.
I use both.
epdview is fast and simple and easy to use, but I've found that there are some PDFs that it just can't display properly (or at all, sometimes).
zathura so far has been able to display everything I've thrown at it, and it's very fast. It doesn't, however, have the usual menus and buttons that most GUI programs have. You have to memorise the key-bindings (most of which are obvious). I'll probably switch to this as my default PDF viewer.
Both are packaged for Debian, and probably for other distros.
epdview will almost certainly be packaged - it's been around for years and is based on the poppler PDF rendering library.
zathura is newer and seems to be based on it's own fork of
epdfview hasn't been maintained since 2011 (see What happened to ePDFview‽). qdfview seems like a good replacement for it.
It has a scrollbar for the Thumbnail sidebar, but seems to only display a scroll bar in Continuous view mode (
View menu ->
Continuous, or Ctrl+7.
Debian package info says:
Description-en: tabbed document viewer
qpdfview is a simple tabbed document viewer which uses the
Poppler library for PDF rendering and CUPS for printing and provides
a clear and simple Qt graphical user interface. Support for the DjVu
and PostScript formats can be added via plugins.
Current features include:
- Outline, properties and thumbnail panes
- Scale, rotate and fit
- Fullscreen and presentation views
- Continuous and multi-page layouts
- Search for text (PDF and DjVu only)
- Configurable toolbars
- SyncTeX support (PDF only)
- Partial annotation support (PDF only, Poppler version 0.20.1 or newer)
- Partial form support (PDF only)
- Persistent per-file settings
- Support for DjVu an**d PostScript documents via plugins