We've liked another member of the ScanSnap family before, so its not surprising that its cheaper, smaller and more-portable little brother also turned out to be pretty great. It basically wins on two fronts: it's really tiny and only needs a USB cable for power, so it's negligible to take with you, and creating a PDF document involves loading the paper and pressing a button. When you're done, you can choose to scan it to a folder, email, send it directly to Evernote, plus several other options.
The whole process is really simple, it works quickly, and it's really tiny. If you're dealing with tons and tons of documents, you'll probably want something with a bit more power, but when portability and simplicity come into play the S1100 does a great job.
The ScanSnap S1100 retails for about $249.
ScanSnap S1100 [Fujitsu]