when you import a 2page.pdf - how do u see the second page
The import dialogue box will show you the pages, and you select the
ones you want. They will end up as separate layers in gimp.
when you export a 2page.pdf - how do u save the 2nd page
this sucks!
make sure all layers are visible, and see the options in the export
dialogue - in particular for Layers as Pages and the one to reverse
order.
NOTE gimp is a BITMAP or RASTER editor, and PDF is a VECTOR format.
Loading a PDF into GIMP in general is lossy, some detail is thrown
away. I use xournal to edit PDF files e.g. to sign them (on Linux at
least).