The iPad already has loads of great apps available for it.

Some are universal, optimising themselves accordingly for your iPad or iPhone.

Some are 'upgrades' of iPhone apps, reworked for iPad. And some are entirely new apps, designed specifically for Apple's table.

We worked our way through the App Store and furiously tested a huge (digital) pile of apps, before coming up with our 40 best paid-for iPad apps.

1. 1Password for iPad (£5.99)

Online security is increasingly important, and it's recommended you use 'random', complicated passwords for logins. The thing is, they're tough to remember, which is why 1Password is a handy app to install. It enables you to store website names and passwords for automatic login.

Unlike the Mac version, 1Password for iPad doesn't integrate with Safari, instead using a built-in browser, but it's a no-brainer for safeguarding details you don't want anyone else to have access to.

1Password

2. Air Display (£5.99, universal)

If your iPad's sitting unused in your office while you work on your Mac or Windows PC, Air Display enables you to turn your tablet into a second display.

It's likely using VNC, so updates aren't fast enough for video, but the app's fine for palettes, inspectors, IM apps and browser windows, and although you can move your mouse cursor to the iPad, you can also control your computer's windows via the touchscreen.

Air display

3. Air Sharing HD (£5.99)

Apple seems to think email and iTunes are the best ways to get documents on and off your iPad. If you want something better, Air Sharing HD enables you to wirelessly copy across files via Finder or Windows Explorer, or to grab attachments from email accounts. Items within the app can be managed, viewed, opened in another app, emailed, or printed via a shared printer on your network.

Air sharing hd

4. Air Video (£1.79, universal)

Air Video Free grabbed a slot in our best free iPad apps feature, but the paid-for Air Video release is even better. Lacking restrictions, it enables you to browse full playlists and folders from computers on your network running the free Air Video Server, enabling you to stream video.

The app uses live conversion when necessary and works with AirPlay if you have an Apple TV.

Air video

5. FlipTime XL (£1.19)

In our opinion, FlipTime for iPhone is the best clock app ever designed. The iPad version is pretty much identical, aping old-school flight info boards and including alarms and a 'flickable' calendar. Luckily, this means it's still utterly brilliant.

Fliptime xl

6. FTP On The Go PRO (£5.99, universal)

FTP On The Go PRO is used to view web and office files on a server, and to resize and upload images from your photo library. There's also a built-in editor and browser, making the app almost resemble a 'lite' iPad version of Panic's Coda.

FTP on the go

7. GoodReader for iPad (£2.99)

If you want a good PDF reader for iPad, it makes sense to buy one called GoodReader! Luckily, the app lives up to its name. You can connect to various services (or dump documents into the app via iTunes file sharing), and the app is effective for reading PDFs (and also other text files, such as Office and iWork documents). The app now also enables annotations.

GoodReader

8. Instapaper (£2.99, universal)

If you often find yourself thinking "I'll read that later", but you never do, you need Instapaper. It enables you, with the help of a bookmarklet, to fling web content to the service, which then syncs with the iPad app. This provides you with a focused, high-quality reading experience on a device that's great for reading. A number of iPad and iPhone apps also offer 'send to Instapaper' support.

Instapaper

9. Korg iElectribe (£5.99)

If you're lucky, you might be able to pick up an Electribe-R on eBay for £100. By contrast, Korg iElectribe costs six quid and yet it's essentially the same piece of kit that's revered by dance musicians. While it's great fun for mucking about with, the app also has serious potential for live performance and recording duties.

iElectribe

10. LogMeIn Ignition (£17.99, universal)

Yet another universal app that suddenly makes sense on the iPad's larger screen, LogMeIn Ignition enables you to access and control computers remotely. Set-up is simple and the app is usable, assuming you've a reasonably fast internet connection.

The iPad version also helpfully includes Command+Tab and Command+' shortcuts for Mac users, assuming you have the slightly cryptic 'Alt=Command, Windows=Alt' setting selected in LogMeIn Ignition's 'Remote Control' preferences.

LogMeIn

11. Numbers (£5.99)

The best of the three iWork apps for iPad, Numbers feels right at home on Apple's tablet. The intelligent keyboard is a joy to use when entering data, and you can create forms that make adding data to tables a cinch. If your needs are modest, this app can rival Bento for data management, and it's capable of exporting to Numbers for Mac, Excel and PDF.

Numbers

12. OmniGraffle (£29.99)

OmniGraffle feels right at home on the iPad, using the touchscreen as a canvas. The diagramming tool - which you can use to create flowcharts, sketch out ideas, and even plan an office floorplan - is intuitive and straightforward, enabling you to make full use of multi-touch gestures to draw, drag and style shapes.

OmniGraffe

13. Pages (£5.99)

Another iWork app converted to the iPad, Pages is a successful word processor, offering some interesting multi-touch gestures for editing content. In combination with a keyboard dock or Bluetooth keyboard, it's possible to do real work on the iPad using Pages, even if the app lacks some features from the desktop version.

Pages

14. Photogene for iPad (£1.79)

Photogene is similar to the iPhone version in being a simple tool for making quick image edits: cropping, resizing, straightening, levels adjustment and sharing. Usefully, the app includes session restore and the ability to revert any section's edits, ensuring you can experiment without fear.

Photogene for ipad

15. Pianist Pro (£2.99)

This upgrade of MooCowMusic's iPhone app is a useful tool for musicians. On the iPad, the piano keys on Pianist Pro are large enough to actually play a real song. There's a selection of sampled piano, organ and synth sounds included, along with an arpeggiator, a basic drum machine and recording functionality, making this a suitable app for laying down quick demos.

Pianist pro

16. SketchBook Pro (£2.99)

We're big fans of SketchBook on the iPhone, and this high-def version, SketchBook Pro, makes it even easier to sketch out an artistic image. The tools are amazingly advanced, mirroring what you might see in Photoshop, Painter or in a real artist's shop. (Image credit: Michael Heald, fullyillustrated.com)

Sktechbook pro

17. Soulver (£3.49)

It's hard to categorise Soulver - the app is a mixture of calculator, spreadsheet and the back of an envelope. It enables you to make calculations in plain English, using a multi-line display. The large, friendly keyboard includes useful features such as percentages and user-definable variables, and Soulver for iPad therefore comes recommended as an alternative, superior take on a calculator.

Soulver

18. Things (£11.99)

Things is a task manager for iPhone and Mac, well-regarded due to its innovative, efficient means of filing items, which helps you focus. New to-dos are collected in your inbox, and you define what you want to achieve today, soon (via the 'Next' category), soonish (via 'Scheduled') or at some point in the distant future ('Someday'). On the iPad, Things boasts an intuitive interface, making using the app almost effortless.

Things

19. Twittelator for iPad (£2.99)

Twittelator for iPad is a Twitter client which makes full use of the iPad's screen space. On the left is your feed; on the right is everything else: messages, mentions, searches and drafts. This means you don't leave your feed to do other stuff. There are also loads of options for power users, but the default set-up's fine for anyone who doesn't like to tinker.

Twittelator

20. Weather Station Pro (£1.19)

It's not the most feature-packed weather app, but Weather Station Pro is one of the best-looking ones. It provides current conditions for user-defined locations; for one selected location, you also get a five-day forecast, sunrise and sunset times, and local time information, making the app suitable for use as a clock when your iPad's docked.

Weather station pro