When you scan a document, chances are the resultant PDF file is merely an image of the original document without a searchable OCR layer. PDF images are not nearly as useful to a law practice as are searchable PDFs. While many scanning applications can automatically convert PDF images to searchable PDFs as part of the scanning process, doing so can slow the process to a crawl. Anything that slows the scanning process will make you or your staff less likely to scan everything that comes into the office. Discouraging scanning is the last thing you want to do.
One answer is to buy or upgrade your version of Adobe Acrobat from Standard to Professional. Standard does a great job of applying OCR to PDF images and turning them into searchable PDFs. But it does so one document at a time. If you need to convert a whole folder worth of documents, the process is tedious and time consuming. But Acrobat Professional allows batch processing of a large number (potentially hundreds) of documents at a time. For this feature alone, the upgrade from Standard to Professional is worth the price (typically in the $160 range per license). There are also other benefits relating to the creation of forms, redacting functions, document comparison capabilities, etc. Although a bit out-of-date, this blog post from Acrobat for Life Sciences details the steps to set up batch conversion of PDF images to searchable PDFs. There is a similar post from the ABA.
Of course, batch OCR processing of multiple files is memory and processor intensive, so you will want to do this on a spare computer or at times when you are not using your computer for other functions. I know a tech-oriented appellate specialist in Detroit who gets extra duty out of his inexpensive Intel Atom-powered netbook by using it for scanning and batch OCR while at the office, then unplugs it from the office network and takes it on the road while traveling. That's squeezing great value out of a sub-$400 computer. Since learning of this idea, I've also done it with great success using my Toshiba NB205 netbook and an old spare copy of Acrobat 6 Professional I had in my junk drawer. You don't even need to leave your desk to do this because you can use any of several methods (Windows Remote Desktop via Live Mesh if the netbook has XP Home, LogMeIn, VNC, GoToMyPC, etc.) to remote into the netbook (or any spare computer) from your primary PC to open Acrobat and trigger the batch OCR process. As a Live Mesh user, I typically use Remote Desktop for this purpose.