In multifunction or all-in-one printers, fax machines, photocopiers and scanners, an automatic document feeder or ADF is a feature which takes several pages and feeds the paper one page at a time into a scanner or copier,[1] allowing the user to scan, and thereby copy, print, or fax, multiple-page documents without having to manually replace each page.
Most copiers allow scanning on the flatbed or platen (the "glass") or through a document feeder. The vast majority of fax machines have an ADF, allowing the unattended sending of multi-page faxes. ADF is so ubiquitous in fax machines that some fax machine owners use the machine as a scanner, faxing multi-page documents to themselves. Document feeders are described by speed, in pages per minute or ppm, and capacity, usually in a range from 10 sheets to 200.
There are two kinds of document feeders capable of two-sided (duplex) scanning: a reversing automatic document feeder or RADF scans one side of a page, then flips it and scans the other side. A duplexing automatic document feeder or DADF scans both sides in one pass. The advantage of the DADF is faster speed for two-sided originals. RADFs and DADFs are rated in images per minute (IPM), the number of sides they can scan each minute; this may depend upon the resolution being used (rather than the maximum resolution supported).
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Scanning large documents requires a storage solution. Initially, the scanner stores the document on the hard drive of the computer to which it’s connected. This location, however, prevents file sharing and leaves the digitized document vulnerable to hard drive failure -- if the hard drive on which the files are stored dies, then all the documents are lost. Use a cloud-based storage system for archiving the documents quickly and making them accessible to others. A service such as Microsoft’s SkyDrive or Apple’s iCloud quickly makes your scanned documents available on any of your compatible devices. If you need to share the documents between users, you’ll need services such as Google Drive that allow sharing of files with other Google users. Large volumes of documents require scalable solutions, such as Rackspace’s 10-cents-per-GB Cloud Service or Amazon’s $500-per-year, 1 TB storage upgrade to Cloud Drive.