The other day, I needed to scan a bunch of printed papers into a PDF file that I could send electronically. I didn't have anything installed on my PC that could do the job, so I was about to dig out my copy of Adobe Acrobat Professional, which can do it admirably. But although they're very capable, Adobe's products are huge, and I only wanted to scan a handful of pages. I didn't need all the other functionality that comes with the suite.
In the past I'd seen recommendations for a freeware application called Scan2PDF, so I decided to try it. And, to my surprise and relief, it worked just fine.
You can get Scan2PDF from http://www.koma-code.de/index.php?option=com_content&task=view&id=39&Itemid=82. Despite the fact that the web page hasn't been updated in years, the software works just fine on Windows 7 and older version too. It's just a 1.5 MB download, is free from malware according to VirusTotal, and is available as a portable version so you don't even need to install anything.
Once you've unzipped the downloaded file, run scan2pdf.exe and the simple interface appears, as shown below. Click the Scan button to scan each page (you'll need to have your scanner installed first, along with the necessary drivers). When you're done scanning, click the Save icon and you get a PDF of your scanned documents. It's as simple as that, though you may wish to check out the various options before you start scanning as they can't be applied retrospectively.