This post will look at drawing apps. While some of the painting apps will allow you to draw as well as paint, the apps below are mainly designed for drawing. Some will also include tools for vector based drawing as well as freehand. In general you will find that these apps have all or many of the tools you would find in desktop applications such as Adobe Illustrator or CorelDraw. Some of these apps have desktop counterparts that you can also purchase to move your files back and forth between device and desktop. In other cases some of the apps will export to a format that can be opened in desktop applications.
As alway, be sure to look the the descriptions and reviews to determine if the app will preform and save a file for your intended use.
Note: If you are looking for painting and drawing tools together have look at the painting apps overview blog entry.
iDraw
iDraw is a powerful vector based Illustration app for your iPad. All of the usual vector tools are here, Vector brushes, customizable shapes, lines, geometry settings, path controls for combining multiple shapes with all the usual options, bezier pen for editing points, cures and lines. There are layers, text with styles options, gradient editor color picker and grouping options. And so much more!
You can export the files you have created as editable PDFs or SVG files, or copy and paste the work into other iPad apps. You can also email designs as JPG, PNG, or as vector based PDF and SVG files. You can also Dropbox.com your files for easy transfer to desktop.
If you are an Illustrator user, or use to drawing in other vector based software this app might be just what you are looking for.
There are two versions one for the iPad 9.00 and one for your desktop, 25.00
Watch a YouTube Video Overview: http://www.youtube.com/watch?v=snYU1eT8COM
The Creator’s Website: http://www.indeeo.com/idraw/
Check it Out at the Apps Store: https://itunes.apple.com/us/app/idraw/id363317633?mt=8
Inkpad

The app is 5.00.
Watch a YouTube Video Overview: http://www.youtube.com/watch?v=VU2UFmrDGk4
The Creator’s Website: http://www.taptrix.com
Check it Out at the Apps Store: https://itunes.apple.com/us/app/inkpad/id400083414?mt=8
SketchBook Ink

This app is more for creating line drawings that you could bring into other painting software on your desktop, rather than for creating paintings on the iPad. Although you can do so if you wish too. There are no layers and the brushes are all preset with no ability to customize.
Sketchbook Ink has a very high output resolution. You can export images to iTunes at up to 101.5 megapixels (8727 pixels x 11636 pixels). Saving to your Photo Library or e-mail will save up too 12.6 MP. Either way exported files are PNGs, so the image quality will be very good. you can even export a transparent PNG.
The price is 5.00
Watch a YouTube Video Overview: http://www.youtube.com/watch?v=2HzZst6WoyM&feature=share&list=UUqqzJUfJ_ofn8ZmL7dBdUwg
The Creator’s Website: http://www.sketchbook.com/news/announcing-sketchbook-ink.html#.UV8kgL_kFEA
Check it Out at the Apps Store: https://itunes.apple.com/us/app/sketchbook-ink/id526422908?mt=8
SketchTime – Quick Sketching & Photo Tracing

Highest resolution export depends on your device (iPhone4: 1000×1500, iPhone5: 1000×1778, iPad: 1200×1600, iPad3: 2400×3200), and supports transparent backgrounds. There is a palm rest for iPad users. Has playback option for recording your actions.
This is a relatively new and very highly rated app. Apple Inc. says “SketchTime simplifies sketching down to its essence”
The price for the app is 2.00.
Flickr stream for images created in SketchTime: http://www.flickr.com/groups/sketchtime
Watch a YouTube Video Overview: http://www.youtube.com/watch?v=ddSsVysE-iw
The Creator’s Website: http://sketchtimeapp.com
Check it Out at the Apps Store: https://itunes.apple.com/us/app/sketchtime-quick-sketching/id500522911?mt=8
Drawing Pad

This app costs 2.00
Watch a YouTube Video Overview: http://www.youtube.com/watch?v=bEU0EmiZcAk
The Creator’s Website: http://drawingpadapp.com
Check it Out at the Apps Store: https://itunes.apple.com/us/app/drawing-pad/id358207332?mt=8
Paper by Fiftythree

The basic app is free, you will get a nice ink pen, lots of colors, an eraser and a few notebook styles to get you started. There is also an idea book included too. Which is nice to get you thinking about how you can use the app.
There are some in-app purchases that allow you to load up your Paper app in the way you prefer to use it. There are five individual tools each priced at 2.00. You can get 4 of them for 7.00 if you buy the Essentials pack. The Mixer add–on is not part of the Essentials so you would have to add that as will if you wanted it. If you got it all you would pay 8.99 for app. If you like to doodle or illustrate ideas when taking your notes this app might be what you are looking for.
Watch The Vimeo Video Channel for more tutorials: http://vimeo.com/37254322
The Creator’s Website has intro video too: http://www.fiftythree.com
Check it Out at the Apps Store: https://itunes.apple.com/us/app/paper-by-fiftythree/id506003812?mt=8
iPastel

You can store up to 10 works in progress and then export your creations to your camera roll. Not sure she the file size is for this app, could find no reference for it, just said fullscreen drawing.
The free version comes with ads and no ability to merge or swap layers. You will have to pay 3.00 for the premium version to enable layer those and kill the ads. There is also a version for your desktop.
Watch a YouTube Video:
The Creator’s Website: http://www.norbyte.com/ipastels/
Check it Out at the Apps Store: https://itunes.apple.com/us/app/ipastels/id489302558?mt=8
I use sketch.io and Kleki online drawing tools. no need the download and install.
I’ve been very happy with my XP-Pen ( https://www.xp-pen.com ) drawing pad with digital pen stylus.
Works perfect with Kleki and sketch.io.