Some ideas are better scribbled down than typed out.
Paper basically turns your iPad into a cocktail napkin for jotting down sketches and ideas. The app is free, though there are a handful of in-app purchases that allow you to expand the tools in your palette, which turns that cocktail napkin into a blank canvas.
Launch Paper and you're presented with a row of Moleskin-like notebooks, bringing to mind Microsoft OneNote's layout. (The team behind Paper previously worked at Microsoft on the ill-fated Courier tablet.) Paper is blissfully devoid of menus, submenus, and other busy blocks of buttons. Three buttons sit below the notebooks: Delete, Share, Add. You can share an entire journal via e-mail (as a PDF) or send it to another app. When you create a new journal, it gets added directly to the right of the one centered on the screen, and you can tap-and-hold to drag a notebook to another spot. Tap the small "i" button in the upper-right corner of a notebook to give it a title and new cover (either from a photo or one from Paper's collection).
Tap on a notebook to open it. You can then swipe sideways to flip through its pages. Tap on a page and it opens in full-screen. When viewing in full-screen, you can swipe from either the left or right edge to flip page to page through a journal. Pinch to close a journal.
When viewing a journal, the three buttons -- Delete, Share, Add -- remain. But in this view, the Delete button removes the page you are viewing; the Share button lets you share the page via Tumblr, Facebook, Twitter, and e-mail (or save it to your Camera Roll); and the Add button drops in a new page. Tap-and-hold a page to drag it to another spot in the journal. Also, while tapping-and-holding on a page, you can pinch with your other hand to close the current journal and then drag the page to another journal. And if you tap-and-hold on the Add button, it lets you duplicate a page or journal.
Last but not least among Paper's gestures is undo or, more accurately stated, rewind. While there is an eraser tool (which we'll get to shortly), you can undo previous scribbles or brush strokes by moving two fingers in a counterclockwise direction.
When viewing a page in full-screen, swipe up from bottom edge to reveal the tool tray. The free app starts you off with an eraser, a fountain pen and nine ink colors, and four grayed-out tools. Inking felt quick and accurate with my finger, and Paper suggests you use a stylus for finer control. Tap on one of the grayed-out tools and Paper makes you an offer. For $1.99 each, you can buy a pencil for sketching, a marker for outlining, a ballpoint pen for writing, or a watercolor brush for painting. You can save a buck by getting all four for $6.99.