Some time ago I installed the official version 9.1 of Acrobat reader on my 64-bit Ubuntu desktop. If I remember correctly I had downloaded the distro-independent installer from Acrobat's website.
A few months ago an update to Firefox caused it to crash if Firefox were open at the same time. It took me a while to realize that was what caused it. At first I just realized that if I ever tried to open a PDF file from a web page it crashed, but other times it worked fine. Finally I realized the other times were any time that Firefox wasn't open.
A bit of Googling led me to a few threads about a known issue with Adobe 9 that caused this. Well, kudos to the Adobe guys because they listened, found and fixed the problem. Adobe 9.1.2 fixes the problem.
Since I'm running a 64 bit OS and Adobe only releases 32 bit Linux versions, I had to force the install of the Debian package by doing:
sudo dpkg -i --force-all AdbeRdr*
Now, no more crashes with PDF's. Yes, I know I could use eVince in Linux to natively display PDF files, but I've found a few display bugs with more complex PDF's and when Adobe is kind enough to produce a Linux version, I might as well use it.