Adobe reader can show two pages up, but they must be continuous pages, is there any option to show two pages, for example, page 1 and page 5 side by side?
Use STDU Viewer. It's free and has split view function like in MS Word.
Windows > Split View
This has been an issue I have been dealing with too. Most of the PDFs I read are scientific articles and most of the time you need to read the article and watch a figure from the same file. I was always looking for some PDF viewer that could do something as simple as splitting the view. Adobe Acrobat Pro offers some of this in the menu
Window -> Split vertically but the problem is that the two views are synchronized: when you scroll one side the other scrolls too, not letting you see two parts of the document. Having the same PDF in two different windows is not optimal and somehow annoying (e.g. when switching windows).
From this same post (Alex) I found that STDU (v 1.6.206) could do non-sync splitting but the feature was only horizontally, misusing the great advantage of modern wide screens. At the time I discovered it, I remember emailing the STDU support to ask for this feature. I don't know if they heard my plea or just came with the idea themselves but from version 1.6.294 (at least) STDU can do vertical splitting, and you can move and zoom in independently in both panels. This was a great addition. Besides that, STDU also supports tabs and session saving.
If STDU developers are reading this, thanks a lot!
Another viewer with this feature is Foxit Reader (on Windows; the Linux version doesn't seem to have it). It's enabled by
View > Split > Vertically Split, but you can also add it to a quick access toolbar.
The only way that I know of is to use a program like PDF Split & Merge to create a PDF that consists of only these two pages.