All browsers require some maintenance at one time or another, or troubleshooting whether it's Safari, or Chrome, Firefox.. etc. I've yet to have any issues with Safari 6 on Mountain Lion.
For the PDF issue...
Open the Finder. From the Finder menu bar click Go > Go to Folder
Type this exactly as you see it here: /Library/Internet Plug-Ins
Click Go then move the AdobePDF Browser plugin (or just PDF Browser plugin) from the Internet Plug-Ins folder to the Trash. Quit then relaunch Safari to test.
For autofill. Try troubleshtooting the Safari.plist (preferences)
Back to the Finder. Go > Go to Folder.
Type this: ~/LIbrary/Preferences/com.apple.Safari.plist
Click Go the move the Safari .plist file to the Desktop. Quit then relaunch Safari to test.
If that that helped the autofill issue, move the .plist file to the Trash. If not, move it back to the Preferences folder.
If that didn't work, Go > Go to Folder.
Type this: ~/LIbrary/Caches/com.apple.Safari/Cache.db
Click Go the move the Cache.db file to the Trash. Quit then relaunch Safari. Try autofill.
I followed your step 1: moving the adobe pdf browser plug in to the trash. Well, I almost followed it. I removed the file that looked closest to it -- the adobeviewer something or other plug in.
Then I couldn't do step 2, because my keyboard doesn't have the squiggly line key. Should I just reinstall adobe?
I too suffer frrom not getting Adobe pdfs to open in Safari
I folowed your instructuions for Adobe PDF and got a no file foundresponse.
I then searched withSporlight and again drew a blank
I found AdobePDFViewer PLug ins but when I opend the folders were empty except for several p.lists
I am using Adobe Professional 8.3.1 andalsoo Acrobat ReaderX 10.1 with Snow Leopard
Am I causing a conflcit or saddled with out of date versions?
Works fine with Chrome
This worked for me with a few caveats, which may be helpful for others
When I first tried, I found that I did not have the permissions. So I had to close down and reboot as Administratr, though I am both administrator and user. Minor point
The nameof the file was not exactly correct. but recognizable so I trashed it
But then it didn't work until I emptied the trash