When you're travelling, keeping track of all the little pieces of paper you accumulate becomes a bit of a pain -- especially expense receipts, receipts for gifts you've bought and so on.
Your smartphone can help out with this though -- a new breed of 'scanner' apps let you use your phone's camera to snap a picture of a document and then have it automatically cleaned up and turned into what looks like a photocopy of the original document.
"But couldn't I just do that with the standard camera app in my phone?" you might be thinking. Apart from the fact that these apps correct all sorts of problems with a traditional smartphone picture (perspective distortion, whitening of pages that have come out grey through the camera, etc), the additional value they bring is that they can upload your documents to online services like Dropbox, Evernote or Google Docs so that they're automatically backed up and synced to your laptop or desktop PC.
Of course, that's a great way to back up copies of your passport and ID cards if you've gone on a trip and forgotten to take copies of them before you go.
Once your document is uploaded as an image to Evernote, its text will be OCRed by Evernote's servers and will be searchable through the Evernote app -- very handy if you upload business cards and then use Evernote as your searching app. Google Docs offers a similar service, except that the end result is that you search documents through their web interface, rather than a desktop app.
Smartphone scanner apps are also a great way to send documents to people when you're on the road and don't want to have to pay for a hotel or post office fax machine. Some of these apps let you 'scan' multipage documents, by taking consecutive photos of each page of a document, and save them as a PDF to your phone (which you can then email). If you couple this with an internet-based email-to-fax service like Utbox, you have a fax machine in your pocket with very cheap usage rates.
The best document scanner app for iPhone
Genius Scan makes scanning a document an extremely simple process: take a photo with the camera; the app automatically detects the document's edges for you (and then you can manually adjust them by dragging), then the final result is shown with automatic corrections made to the image such as lightening the background and correcting perspective distortion.
It's not the most fully featured scanning app available for iPhone, as it can only send scanned documents to email (not Dropbox, Evernote or Google Docs) but of the various apps we tested, it's by far the easiest to use and most reliable. You can still send documents to Evernote and Google Docs by using their email-in services (see How to email files to Evernote, and how to email files to Google Docs).
A more fully featured scanning app is Scanner Pro, which supports saving scanned documents to Evernote, Dropbox and Google Docs -- but we didn't like the user interface as much. It's considerably more complicated than Genius Scan.
The best document scanner app for Android
DocScanner can scan your document for you and save it to Evernote or Google Docs. One handy option is the ability to select the actual paper size of the document you're scanning so that when it is viewed on a computer or printed, it'll be shown at a lifelike size.
It's also able to email a multipage document as a PDF, or as multiple JPEG files in a ZIP archive.
The best document scanner app for Blackberry
Price: Free app; first five scans are free.
Where to get it: Blackberry Appworld
We couldn't find an app for Blackberry that offers general document scanning like Genius Scan or DocScanner. However, there is an app called Cognicard which focuses on scanning business cards and then providing you a Vcard by email with the information recognised from the business card.
The app is free to download but only comes with five free business card scans. After that, you have to buy credits, ranging in price from $US5 for 20 credits to $US25 for 150 credits (one credit equals one business card scan.)
The best document scanner app for Windows Phone 7
Handyscan wins the "best for Windows Phone 7" award rather dubiously -- as far as we can see, it is the only app available at the time of writing for scanning docs with your Windows Phone 7 handset.
Its main claim to fame is that it has a 'typewriter' tool which lets you type into fields on forms. Of course, if you had the form there to scan with the phone, one wonders why you wouldn't just fill in the form by hand.
After you take a picture of the document with the phone in your Win Phone 7 handset (we used an HTC Mozart), the program gives you three options for optimising the image, which appear to be rather crude image adjustment presets. You can crop the image, however the app only crops in a rectangle -- it doesn't have the draggable corners like other document scanning apps that allow the app to correct perspective distortion for you.
Once you've scanned a page with Handyscan, you can keep scanning more pages to create a multipage document. The scans can be saved as JPEG (for single page scans) or PDF (both single page/multipage), and then saved to the phone's photo library, inside the app, or sent by email.
Disagree with our choices? Let us know why in the comments and we'll gladly consider other apps for our "best of" nomination.