I have nspluginwrapper-1.1.2-4.fc10.i386.rpm, AdobeReader_enu-8.1.2_SU1-1.i486.rpm (fixed by hand to force the RPM install to work properly as I described in another bug), and mostly other up-to-date packages from Rawhide. When I configure firefox to view PDF files inside a browser window using nspluginwrapper, then browse to a PDF file, then hit the back button to go back to the previous page, npviewer.bin exists, but acroread does not. Instead, it stays running forever, increasing in memory size little by little until eventually it is so large that it hoses the entire machine.
It's a bug in Adobe pdf plugin...I can reproduce it without nsplguinwrapper installed. I'm afraid I can't fix that bug in nspluginwrapper because adobe reader runs as different process and it's separated from the plugin.