Scanners may not be as frequently used in offices as printers or desktop computers, but they are very useful for preserving and storing hard copy documents and their contents. When your office receives a document, such as a signed contract from a client, the fine print of an insurance plan, or a purchase receipt (both of which you do not have soft copies of), you may need to scan the documents and keep the digital copies as backup.
You might ask, why not just photocopy them? There are many things to consider here. First, if you need to keep a soft copy instead of another hard copy of the document, you’ll need to have it scanned. Second, if the integrity of the print or the signatures on the paper will be compromised on the copy (if the pen mark is too faint, the writing may not be visible anymore on a photocopy), it will be better to scan it to preserve the entirety of the document. Third, with a soft copy in hand you can always print out precisely similar hard copies of the documents any time you need them. That should cover the convenience of having an instant hard copy from a photocopier.
Take note that two of the reasons above speak of the importance of preserving the integrity of the original documents, that none of them be missing any visible component when reproduced or stored in archives.