Scanning 
First, a document imaging scanner must have an Automatic Document Feeder (ADF). This device allows a stack of paper to be placed in a tray and automatically brought in one page at a time, much like a fax machine. Scanners without an ADF were designed for graphics and require you to place manually each page to be scanned.
Second, don't skimp on the scanner. It's nice to have the fastest scanner available, but it's more important to consider your budget and the size and volume of paper you have to scan.
Different Classes of Scanning Hardware
There are 4 main classes of scanners to choose from; desktop, workgroup, departmental, and production grade. These classes range based on the volume of pages they can scan, the features they have and cost.
Desktop Scanners: - Approximately 10-20 pages per minute:
An entry level class of document scanners that satisfies low volume scanning requirements and is generally rated for several hundred pages per day. These scanners provide duplex, color and mono scanning at speeds ranging from 15-35 pages per minute. through the automatic that want decentralized scanning to occur at the desktop level. Approximate cost: $400 - $800 USD.
Workgroup/Departmental Scanners: Approximately 15-40 pages per minute:
Workgroup and departmental scanners provide the essentials for most small workgroups who are requiring a more robust scanner that can withstand constant use and provide consistent results on sustained volumes of documents of up to 1000 or more documents per day. There is some blurring of the boundaries between Workgroup and Departmental grade scanners, and this document has combined them since the majority of organizations will probably be looking at something in the 25-45 page per minute category, and will want to consider these types of scanners carefully. Approximate cost: $700 - $2,000 USD.
Production: Approximately 40-90+ pages per minute:
These scanners can range from $9000 to $100,000 or more. Many scanning bureaus and service companies use these types of scanners, as well as high volume environments like hospitals, major corporations, large legal firms, large government offices, medical laboratories, and other high volume, paper intensive environments.
Desktop Scanners: - Approximately 10-20 pages per minute:
An entry level class of document scanners that satisfies low volume scanning requirements and is generally rated for several hundred pages per day. These scanners provide duplex, color and mono scanning at speeds ranging from 15-35 pages per minute. through the automatic that want decentralized scanning to occur at the desktop level. Approximate cost: $400 - $800 USD.
Workgroup/Departmental Scanners: Approximately 15-40 pages per minute:
Workgroup and departmental scanners provide the essentials for most small workgroups who are requiring a more robust scanner that can withstand constant use and provide consistent results on sustained volumes of documents of up to 1000 or more documents per day. There is some blurring of the boundaries between Workgroup and Departmental grade scanners, and this document has combined them since the majority of organizations will probably be looking at something in the 25-45 page per minute category, and will want to consider these types of scanners carefully. Approximate cost: $700 - $2,000 USD.
Production: Approximately 40-90+ pages per minute:
These scanners can range from $9000 to $100,000 or more. Many scanning bureaus and service companies use these types of scanners, as well as high volume environments like hospitals, major corporations, large legal firms, large government offices, medical laboratories, and other high volume, paper intensive environments.
Specifically examining the range of choice within document scanners, there is the entry level Fujitsu ScanSnap, (desktop class) which handles about 15 pages per minute, for around $500, while the Canon DR-9080C, (workgroup or departmental class) which scans 50 pages per minute (ppm) in color and 90 ppm in black is priced at around $6,000. There are scanners priced beyond this, but they are more suited to high volume production environments. Approximate cost: $3,500 - $9,000+ USD.
Sometimes it is cheaper to buy two 20-page-per-minute scanners than one 40-page-per-minute scanner. If you choose this option, you will need to have a document imaging system that can support multiple scan stations.
Nice to have Scanning Features
• Single-pass duplex (two-sided) scanning - learn more below
• Automatic detection of black or color documents
• Barcode recognition (2D and 3D) – This feature often needs to be supported by both the document scanner hardware and the scanning software.
Automatic Document Feeders (ADF) - When shopping for a document scanner, it's a good idea to make sure that the device you purchase has the kind of feeder capacity you need. This is essential when scanning documents in batches where the larger the stack of paper that the ADF can handle the less it needs to be tended to. Most scanners provide automatic sheet feeders that can hold at least 50 sheets.
Color & Monochrome Scanning - Most scanners can handle both black and color scanning; however, it pays to make sure before you buy, especially if you plan to scan illustrated documents.
Single Pass Duplex Scanning - If most of your documents have printing on both sides, duplex (two-sided) scanning can a source of major time savings. Look for single-pass duplex scanning - this means that the document is scanned on both sides simultaneously, rather than having to be scanned twice (once on each side). This can be an invaluable time saver when handling larger volumes (or a backlog) of documents.
Double Feed Detection - A double-feed detector senses the gap between two overlapping pages and stops the scanner when two or more pages are fed at the same time. Special mention of this scanning feature is being made as this is a fundamental component of the scanning hardware. There are basically 3 types of double feed detection to consider when purchasing a scanner all with varying effectiveness.
• Automatic detection of black or color documents
• Barcode recognition (2D and 3D) – This feature often needs to be supported by both the document scanner hardware and the scanning software.
Automatic Document Feeders (ADF) - When shopping for a document scanner, it's a good idea to make sure that the device you purchase has the kind of feeder capacity you need. This is essential when scanning documents in batches where the larger the stack of paper that the ADF can handle the less it needs to be tended to. Most scanners provide automatic sheet feeders that can hold at least 50 sheets.
Color & Monochrome Scanning - Most scanners can handle both black and color scanning; however, it pays to make sure before you buy, especially if you plan to scan illustrated documents.
Single Pass Duplex Scanning - If most of your documents have printing on both sides, duplex (two-sided) scanning can a source of major time savings. Look for single-pass duplex scanning - this means that the document is scanned on both sides simultaneously, rather than having to be scanned twice (once on each side). This can be an invaluable time saver when handling larger volumes (or a backlog) of documents.
Double Feed Detection - A double-feed detector senses the gap between two overlapping pages and stops the scanner when two or more pages are fed at the same time. Special mention of this scanning feature is being made as this is a fundamental component of the scanning hardware. There are basically 3 types of double feed detection to consider when purchasing a scanner all with varying effectiveness.
1.Length-based detection - provides basic detection and is common in introductory scanners for small offices or desktop requirements.
2.Infrared based detection - is much better than length-based and are much more common in workgroup or departmental scanners
3.Ultrasonic detection - is the best possible and is common in most production level models, infrared is better and ultrasonic is the most accurate you can get (although different techniques are required for the fastest, high-end scanners with open transports). Ultrasonic detection is now the norm for most production models, but the technology is finding its way down into the departmental range.
A good imaging system will let you choose from a wide range of scanners and will be flexible enough to bring in documents from outside sources.
