Encrypting Uploaded Files Before Saving to Disk

I am waffling between storing uploaded files in the MySQL database or as files on the local file system. There are many pros and cons for each. I’m leaning toward storing the files on the local file system. If I do, the files must be encrypted since there is a likely chance a file would contain confidential or personally identifiable information.
How would I achieve encryption of files uploaded via the WebFileUploader?