If you don't have installed program for editing PDF documents on your computer, then you can use web application PDFescape which allows you to edit your documents in your browser.
With the new version of Photoshop, you also get a new cropping tool called Perspective Crop Tool which will change the perspective on a image. Check it out, it really is a cool tool.
If you are on a certain data plan on your mobile provider, and don't want to exceed it, you can set data usage warning and a limit which can help you save some of your money.
